HijackThis is a small utility that will list the contents of key areas of the registry and the hard drive. It is very useful for detecting what is loaded/running on your PC, listing installed Browser Helper Objects (BHOs), the default start page, the default search page, and programs/modules that start running automatically, among other things. The list will contain valid entries and might contain invalid (unwanted) entries so you must be careful when deciding what to remove. Removing the wrong thing could cause more problems than you already have.

There is no installation involved with this program. Unzip the file and extract it to its own directory. It can be run from there. You will normally need help from an expert to decide what needs to be removed. Check out the Quick Start tutorial on TomCoyote for more information on running the program and what to do with the results of the scan.

Be sure to check for updates and remember, this utility will list everything it finds, good or bad. Consult the forums for further guidelines.

Useful links:
Major Geeks (Download)
Merijn.org (Author's Website)
Spyware Info (Support Forum)
Merijn.org (Forum List by Author)
Merijn.org (Tutorial by Author)
TomCoyote (Tutorial)
BleepingComputer (Tutorial)