|Can you get into safe mode?|
For windows xp
Go to Start > Run > type msconfig > press enter
Go to Start > type msconfig > press enter
from the console that appears, go to the startup tab and click on disable all.
you may want to keep your firewall and anti virus enabled s find those enteries and enable them.
Dont worry you can enable everything again later if neccessary.
i am not an expert in virus removal so can only advise on applications that i have used and know are good and safe.
Down, install, update and run the following applications.
Spybot Search and destroy
run these and hopefully they will help