Many viruses, spywares, hackers and other dangerous programs use rootkits to hide their existence on the host computer. This means that even if the programs are running, you do not see them appear in the process list. This is very annoying, since you will not know the nature of the malicious software. Therefore some software companies have written up anti-rootkit software to help eliminate the menace. Check them out. If you want more information on how to detect rookit and remove them, check out this site or here.
AVG Anti-Rootkit - Free Anti-Rootkit Software
This is another fine product from AVG. This software removes rootkit effortlessly from your computer. It is free and runs on Windows.
Rootkit Hook Analyzer - Free Anti-Rootkit Software
This software is a rootkit identifier. It finds all the rootkit on a computer and shows them to you. However, some of the rootkits might not be malicious. You need to use your knowledge of rootkits to root the bad ones out. Runs on Windows NT, 2000, XP, 2003 and Vista.
RootkitRevealer - Free Anti-Rootkit Software
This is a free rootkit detection utility from Microsft which allows you to identify rootkit in your NT-based operating system.