There is a new version on FileHippo but I prefer 1.99.1.

Hijackthis is the best single tool we have found to diagnose the health of a Windows system. HiJackThis scans system locations frequented by spyware and hijackers and produces a log file. This log file contains the names of both good and bad programs so discernment is necessary. Best practices:

• open "My Documents". It is best to aggregate all your important files in one location to facilitate burning to CD and DVD. You do backups, don't you?
• File, New, Folder, hijackthis. Keep the root from getting too messy so you can find things,
• download from http://filehippo.com/download_hijackthis/ and put it in the folder My Documents/hijackthis
• run hijackthis
• Do a system scan and save a log file.
• rename the logfile to todays date in iso format, e.g. 20060903.log. Iso dates sort properly. You may want to compare results at a later date.
• go to http://www.hijackthis.de/
• copy (Ctrl-A, Ctrl-C) and paste (Ctrl-V) into the textbox
• Analyze
• click the "stars" to learn more

If the analysis reports "Nasties" there is work to be done. You can "delete" the nasties in HJT, but more than likely there is some serious cleaning to be done.