Intel Pentium D 940 Dual Core 3 2 GHz 4M/800 775 SL94Q

It is not on the list of supported CPU's http://processormatch.intel.com/CompDB/SearchResult.asp...

that list only supports duel core and newer

Yes my guess is that it has something to do with memory controller on CPU or not.

None of those CPUs have an IMC. I'm not sure if the P45 can support the older P4s. Support for tech that old might be gone. Seeing as it does support newer CPUs, why bother with something that ancient? Just get whatever CPU you can afford and dump the old P4.

The D's may be old, but they are still good enough for a lot of home computing tasks, especially to people on low budgets.

Perhaps, but its a massive heat/power hog. If he sells that for $20 on his local craigs list, and puts another $30 up, he can get the E3300 for $50 shipped from newegg right now.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Should be just fine for home use, and will consume less power and emit less heat then that 940.