Hi,
I have had a similar prob a while ago and the I did find a way to get things back to normal, hopefully this advice helps ...
Download Dr.WebCureIT (on a clean computer)
Then write it to a disk (so that the virus cant change the Dr.webcureit file)
And run the Antivirus, it should remove the virus and enable you to put other antivirusses on your pc.

Not too sure about IE but this should work for the AV prob, if not then tell us

Best of luck!

OOOOOh yeah, dont forget to run Dr.WebCureIT in safe mode(F8) and not in normal mode...

If you remember which antivirus program you had installed. Go to their website and download the remover for whichever version of antivirus software you had and run that in safe mode. As for IE 8, I believe your disk would have the earlier version IE 7 or 6 as IE 8 was an update in SP3. Once you have removed every trace of your old antivirus software (registry entries, dll files) it should let you install any antivirus you want.

Thank u for your great advice but unfortunately it doesnt work
My windows was severely infected ,I said (was)because I instaled a new windows XP professional SP2 And so putting an end to all my machine suffering ,I instaled an anti virus removed all the viruses.
the problem was solved

One of my favorite Virus fighting tools is a bootable rescue cd that comes with Kaspersky Antivirus. So far it has saved one system that had been infected by worms and it even boots up with network support to update the defintions. Plus it just seems cool to boot the computer into another operating system off of a cd.