Okay – you should have a folder in the programmes list called Windows Explorer – open that.
Then at the top of that you’ll see – furthest to the right – the word ‘Help’. Click on it 
Then click on ‘Help and Support Centre’.
Under ‘Pick a Task’ on the right-hand side, click on ‘Undo changes to your computer with System Restore’ or words similar.
It should have a radio button ticked saying ‘Restore my computer to an earlier point’.
Click that, and on the calendar that comes up, pick the last day your e-mail was working right. Then let System Restore do its thing and reboot.
If you’ve installed programmes since then you’ll need to reinstal them, but you won’t lose any e-mail or documents.
Provided it isn’t a bug – as in virus or Trojan of some sort – that should get your Outlook Express working again.
If it doesn’t – just yell!