Microsoft Security Essentials is the name. I would not recommend this 
product for XP machines that have 512 mb ram or less. Here you go for a 
link to the website.
http://www.microsoft.com/security_essentials/

On 9/24/2010 4:26 AM, Joyce A wrote:
> ....
> Wasn't there a very effective "free" antivirus put out by Microsoft 
> though?  The name of it slips my mind...

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