Just a few...
F-Prot anti-virus software (DOS)
http://www.f-prot.com/products/home_use/dos/
Start-up monitor - lets you know when programs register to start on boot
http://www.mlin.net/StartupMonitor.shtml
wget - this link is to a version that works on windows
http://allserv.ugent.be/~bpuype/wget/
Spampal - sophisticated spam flagging
http://www.spampal.org/