|Don't waste any more time.|
Reload the system from clean original cd's.
Get a clean system to download sp3 network install.
Apply it first thing.
Learn and use best practices to avoid this in the future.
Be sure to be cautious on any other media that may re-infect your system.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10