Thanks for the advice, everyone. 
I downloaded Microsoft Antispyware, Spybot Search & Destroy, and Lavasoft Ad-Aware SE, and I was amazed at what they all uncovered. I had a ton of spyware and adware on my computer!
But thankfully, now it’s all gone.
For now. :sarcasm:
I have attached an image of the Microsoft AntiSpyware scan results. Also, I pasted the description for each item below. This information may be useful to someone in the future — for example, a search for “Claria” or “180search” or “ShopAtHome” will bring up this thread.
WindUpdates.MediaAccess
Type: Adware
Threat Level: High
Author: windupdates.comDescription: WindUpdates is responsible for downloading adware.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
NCase
Type: Browser Modifier
Threat Level: SevereDescription: NCase is adware that looks for known URLs and keywords in URLs, and displays pop-up advertisements targeted at related Web sites. nCase also periodically opens non-targeted pop-up advertisements while you are using Internet Explorer.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Browser Modifier: Software that changes browser settings, such as the homepage, without adequate consent.
ShopAtHome.Downloader.A
Type: Trojan Downloader
Threat Level: HighDescription: A Trojan that silently installs other programs without consent.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
eXact.Downloader
Type: Trojan Downloader
Threat Level: High
Author: eXact Advertising LLC.Description: eXact Downloader is a Trojan used by eXact Bargain Buddy and Cash Back to download and install additional components.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Trojan Downloader: A Trojan that silently installs other programs without consent.
YourSiteBar
Type: Spyware
Threat Level: High
Author: Integrated Search TechnologiesDescription: YourSiteBar from IST, the makers of numerous spyware threats, is an affiliate based marketing toolbar.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Spyware: Software that collects information, such as the websites a user visits, without adequate consent. This may include installing without prominent notice or running without a clear method to disable.
WindUpdates
Type: Browser Plug-in
Threat Level: Severe
Author: WindUpdates.comDescription: WindUpdates downloads additional adware and displays pop-up advertising.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Browser Plug-in: A browser plug-in is an application that can be installed within a user’s web browser. Plug-ins can come in the form of a toolbar that is included in your web browser or a search or navigation feature to extra task buttons on the browser. Although most plug-ins are designed to perform necessary functions, many plug-ins are harmful to you computer because they have complete access to your web browser and can modify, spy and redirect any task you perform.
eXact.BargainBuddy
Type: Adware
Threat Level: High
Author: eXact Advertising, LLCDescription: BargainBuddy is a Browser Helper Object that watches the pages your browser requests and the terms you enter into a search engine web form. If a term matches a preset list of sites or keywords, BargainBuddy will display an ad.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
Claria.GAIN
Type: Adware
Threat Level: Moderate
Author: Claria Corporation (formerly known as The Gator Corporation)Description: GAIN (Gator) automatically fills in passwords and other elements on Web forms. Its main purpose is to install an advertising module called OfferCompanion, which displays pop-up advertisements when you view certain Web sites.
Advice: Moderate-risk items have some potential for adverse effect, but may be part of a wanted service. Users may decide to ignore such programs after review.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
WinTools
Type: Trojan
Threat Level: SevereDescription: WinTools’ purpose is currently unknown. WinTools installs an Internet Explorer browser helper object, a URL search hook, and downloads several files in Common filesWinTools. WinTools runs at startup
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Trojan: A program that appears to be useful or harmless but that contains hidden code designed to exploit or damage the system on which it is run.
ShopAtHome
Type: Spyware
Threat Level: Severe
Author: Belcaro Group Inc.Description: ShopAtHome installs an agent in the Winsock layer of your computer. This redirects your Web browser to merchant sites affiliated with ShopAtHome rather than the Web sites you type in or click.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Spyware: Software that collects information, such as the websites a user visits, without adequate consent. This may include installing without prominent notice or running without a clear method to disable.
ShopAtHome.Downloader.B
Type: Trojan Downloader
Threat Level: HighDescription: A Trojan that silently installs other programs without consent.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
IST.ISTbar
Type: Browser Modifier
Threat Level: Severe
Author: Integrated Search Technologies/CDT Inc.Description: ISTbar is an Internet Explorer redirector that modifies your homepage and searches without your consent using an Internet Explorer toolbar.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Browser Modifier: Software that changes browser settings, such as the homepage, without adequate consent.
IST.PowerScan
Type: Adware
Threat Level: High
Author: Integrated Search TechnologiesDescription: PowerScan is advertised through in ordinary web pop-ups, but recently it started to install with help from the the ISTBar adware.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
IEPlugin
Type: Spyware
Threat Level: High
Author: InfoAge Marketing InternationalDescription: IEPlugin is an Internet Explorer browser helper object that monitors URLs, content entered into forms, and local filenames and displays pops-up advertisements.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Spyware: Software that collects information, such as the websites a user visits, without adequate consent. This may include installing without prominent notice or running without a clear method to disable.
eXact.SearchBar
Type: Browser Plug-in
Threat Level: Elevated
Author: eXact Advertising LLC.Description: eXactSearchBar is an Internet Explorer toolbar with standard search features that performs targeted advertising based on the computer usage and the URLs associated with Web pages.
Advice: Elevated-risk items have some potential for adverse effect. Users should review such programs and remove them if unwanted.
About Browser Plug-in: A browser plug-in is an application that can be installed within a user’s web browser. Plug-ins can come in the form of a toolbar that is included in your web browser or a search or navigation feature to extra task buttons on the browser. Although most plug-ins are designed to perform necessary functions, many plug-ins are harmful to you computer because they have complete access to your web browser and can modify, spy and redirect any task you perform.
eXact.CashBack
Type: Adware
Threat Level: High
Author: eXact AdvertisingDescription: CashBack is part of BargainBuddy adware that displays pop-up advertisements.
Advice: High-risk items have a large potential for adverse effect, such as loss of computer control, and should be removed unless knowingly installed.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
eXact.BullseyeNetwork
Type: Adware
Threat Level: Severe
Author: eXact AdvertisingDescription: Bullseye displays pop-up advertisements.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.
AvenueMedia.DyFuCA
Type: Browser Plug-in
Threat Level: Severe
Author: Internet-Optimizer/Avenue MediaDescription: AvenueMedia DyFuCA Internet Optimizer is adware that changes your browser error page. It periodically displays pop-up advertisements from its remote sites and may update itself.
Advice: Severe-risk items have an extreme potential for adverse effect, such as a security exploit, and should be removed.
About Browser Plug-in: A browser plug-in is an application that can be installed within a user’s web browser. Plug-ins can come in the form of a toolbar that is included in your web browser or a search or navigation feature to extra task buttons on the browser. Although most plug-ins are designed to perform necessary functions, many plug-ins are harmful to you computer because they have complete access to your web browser and can modify, spy and redirect any task you perform.
180Solutions.SearchAssistant
Type: Adware
Threat Level: Elevated
Author: 180SolutionsDescription: 180search Assistant displays pop-up advertismenets.
Advice: Elevated-risk items have some potential for adverse effect. Users should review such programs and remove them if unwanted.
About Adware: In general, adware is software that displays advertisements, and may be beneficial by subsidizing a program or service. However, certain adware programs may lack authorization, such as installing without prominent notice or showing ads without clear attribution to their source.