If you can't get it into safe mode using the F8 key, you can try this tip using msconfig:

http://forums.techarena.in/tips-tweaks/1077241.htm

For free anti-malware software, I've used adaware but make sure you get it directly from lavasoft. AVG Free is also pretty good.

If you know the date the problem started, you may be able to use System Restore to return your system files to an uninfected state. I'd review this article first though. http://community.ca.com/blogs/securityadvisor/archive/2008/11/05/persistent-malware-microsoft-s-system-restore-feature.aspx

Since it seems you have access to a different computer, I'd park the infected one for a while, do some research then go in educated.