First get a few things to get you ready for a fresh install:
-(if your copy of XP, assuming its xp is SP1 or no SP)
Xp service pack installer
-(your choice email, and web clients)
-(A up to date firewall, antivirus software)
Now follow these steps:
disconnect yourself from internet
Use Xp sp installer (sorry dont know the real name of the program)
follow Xp install steps.
Once inside xp install firewall, and antivirus software. Then install web clients and email clients.
now connect to the internet and go directly to microsoft.com no where else and install any and all updates for XP. Then update both your antivirus and firewall softwares.
Ocasionaly run spyware software and you should stay clean.
