BleepingComputer Review:

HijackThis is a program that can be used to quickly spot home page hijackers and startup programs that you do not want to start automatically. This program is a not anti-virus program, but rather a enumerator that lists programs that are starting up automatically on your computer as well as other configuration information that is commonly hijacked. Since there is no filter on what it reports, you should research each entry before you remove anything using this tool.  For detailed information on how to use this program, please see the link to the HijackThis Tutorial below.

There are two different downloads available for HijackThis.  The standard download is a MSI installer version that will install the program into the C:\Program Files (x86)\Trend Micro\HiJackThis folder and create a startup menu icon for it.  HijackThis is also available as a standalone EXE file that can be run from any directory or from a removable media device. It is highly recommended that you use the Installer version so that backups are located in one place and can be easily used.
 

Usage Instructions:

Note: You should only use HijackThis if you have advanced computer knowledge or if you are under the direction of someone who does. Improper usage of this pr ogram can cause problems with how your computer operates.

To use HijackThis, download the file and extract it to a directory on your hard drive called c:\HijackThis. Then navigate to that directory and double-click on the hijackthis.exe file. When the program is started click on the Scan button and then the Save Log button to create a log of your information.

For a more detailed tutorial on how to use HijackThis click here:

How to use HijackThis to remove Browser Hijackers & Spyware