The RootAlyzer is a freeware tool that can detects various hiding methods usually used by rootkits. It goes through the file system, the registry and process related lists. When you start RootAlyzer, it performs a very quick scan of a few important places, taking about a second on modern machines. To check the full system, you have the possibility of choosing a Deep Scan.
The program doesn’t required an installation, just run the RootAlyzer exe file and it supports Windows 2000, XP and Vista. More information and download is available from forums.spybot.info