Inspiron 1720 CPU

T9500, 2.6 GHz/800 MHz.

You can use any of the 800 MHz bus Core 2s - but NOT the newer 1066 bus units.

Thanks Husky0894 for the quick reply.  You wouldn't know of a cheap source for them would you?

Thanks again for the help.

The T9500 seems to ballpark between $300-350 a unit just about everywhere.  Beware EBay - the price will be lower, but it's entirely possible you'll end up with an altered or engineering sample CPU and no recourse if it fails to work.