Avira AntiVir Personal

This is, in my opinion, the best and most effective anti-virus program available.
Not only is it the best, it's also FREE for personal use.
Don't believe it? Have a look for yourself --> Independent Test Results
Many other anti-virus programs are bulky, and consume alot of your system's resources.
Last I checked, Avira runs only 2 processes on your computer.
I have seen protection suites that run as many as 17 processes!
While I do recommend that you use the free version, if you like this program,
and it does its' job well... register it it to help keep it the best, and free.
Registration provides you with their great anti-spyware protection as well.
Until then, make sure you check out the 3 anti-spyware programs below.

Avast Anti-Virus Home

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AVG Anti-Virus Free

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SpywareBlaster

This program doesn't remove spyware, it prevents the spyware being installed in the first place.
It works great, your spyware removal scans will come up clean aside from a few MRU lists (browsing history).
As it's a free program, you do have to manually update it (very easy, 2 clicks). Register it for automatic updates.
Make sure to update it about once a week, and 'enable all protections'.

Spybot - Search and Destroy

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AdAware

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