That CPU is not compatible with socket AM2 only AM2+ and AM3.
Actully, Any AM3 cpu can work on an AM2 socket along with AM2+. The issue here though it the Motherboard Bios does not support it and it most likely will not support it due to the age of it.http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?CategoryID=1&DetailID=675&DetailName=Feature&MenuID=24&LanID=9
Now to prove my point about AM3 cpu's on AM2
We All know AM2 came out in May 2006. http://en.wikipedia.org/wiki/Socket_AM2
Well there a motherboard from gigabyte that was released before AM2+ came around. http://www.gigabyte.com/products/product-page.aspx?pid=2287#
Now it says AM2, AM2+, and AM3 support so some might say it's AM2+ socket but if you google this motherboard,
It shows review links that date back to around 2006 for the version 1.0 which was before the AM2+ socket was launched.
So thats how i can prove that Am2 is able to run Am2+ and AM3.
(sorry if this is a little harsh. Had to pull out all the info i had on someone saying the same thing and was not believing me not to long ago.
It took somebody else with an working AM2 motherboard with an AM3 cpu to get the story straight.)
In any case though, It the bios preventing the cpu from working.
All i can say is, return the cpu or buy a new motherboard that can run it. Those are your only options.