up and running

its not fun reinstalling a computer especially when u are concerned in its security.
follow these instructions and you might survive the young life of your clean system:

• format harddrive to be sure all old viruses are killed
• unplugg all connected internet-cables
  
• install windows from your recovery cd
• install all needed drivery
• install SP2 from CD, if you dont have it on CD get it from a frend or your next dealer, but make sure you get it installed before connecting to the net!
• install anti-virus software (my recommondation: antivir)
  
• install anti-spyware software (my recommondation: spybot)
• connect your network/internet devicec
• visit the MS-update site and install ALL security patches
• update anti-visus/-spyware software

this should help you through the rough start...

EDIT:
i have a nice link for you, where you can find a lot of information about software hijacking your system.