Winpooch, an opensource watch-dog for Windows

Winpooch is a watchdog for Windows that helps you increase the security of your computer.  
Winpooch can prevent suspicious programs from doing dangerous actions such as writing to system directories or sensible registry keys. It acts as a powerful anti spyware and anti trojans, and if you have ClamWin installed, you can tell Winpooch to scan every program before it runs. 
This new release provide a cache for antivirus, this prevents from scanning the same file several times and thus increase the computer speed.  It also contains many bug fixes. 
It can be downloaded here

Official HomePage