http://www.methlabs.org/
.WHAT IS IN THE BETA?
PeerGuardian 2 requires no driver installation, yet blocks IP addresses at a far higher speed than was previously available - never above 1% CPU on most test systems. On Windows 2000 and greater PeerGuardian 2 blocks at a kernel level, acting against every protocol used within the windows system. On Windows 98 or Me it blocks TCP only* with the same high performance of the Windows 2000 version.