MS Windows Defender video tutorial
Note: You might need to install MS Silverlight to view this demo
Windows Defender Download here
There are many tools that provide more..(that is for another thread)
Still MS has made this free tool available for Genuine Win XP and Vista end-users

Especially if you are bored to death by Geeky stuff...@ least use this FREE tool from Microsoft
Your puter will luv you too

Windows Defender review
2-spyware.com
We have tested the program on several different setups including badly infected machines and absolutely clean computers that were never infected with any viral parasites, spyware and malware threats. Tests revealed that Windows Defender is an effective, reliable and easy-to-use product that does not produce false positives and provides sufficient protection against most types of spyware, adware, browser hijackers and other malicious pests
Credits: Microsoft and 2-spyware.com