Hi shanzay
You need to boot up your PC and tap the F8 key before windows starts...
From the list that appears, choose: "Safe mode with Networking".
Go to AVG website and download their two Products:
-AVG Anti-Virus Free Edition 7.5
http://free.grisoft.com/doc/downloads-products/us/frt/0?prd=aff
-AVG Anti-Spyware Free Edition 7.5
http://free.grisoft.com/doc/downloads-products/us/frt/0?prd=asf
Then, after installing, run both programs, still in safe mode. This should clear your PC out...
then re-boot. If you're still having trouble you will have to copy all your files to somewhere (CD, DVD, USB or other disk). Re-install windows, install the Anti-Virus & Anti-Spyware products as above (no need for safe mode after a re-install), then you MUST SCAN ALL YOUR DOCUMENTS WITH THE AVG software BEFORE you copy them back to your PC as there may be some infection on those files.
After 1 month AVG, like all the other software out there, will start whinging that you pay some cash (about 20 pounds for a year)... I recommend it as you wouldn't have had all this hassle in the first place..!
Good luck
Cheers
knobby
November 2007