Motherboard / processor compatibility usually comes down to what chipset your motherboard has. In your case, you have the ATI RC415 Northbridge. I couldn't find much information on that particular chipset, unfortunately. But, I did find this page listing the specs of a HP/Compaq computer with that same motherboard.
The Core2Duos require a slightly different power configuration than previous Intel socket LGA775 CPUs, which means that just about all MBs not designed for C2D CPUs can't run them. I'd believe TS's research.
I am in the same boat righ tnow, been researching non stop for the last 24 hours.
Spoke to the Tech guy at Compaq, he said You can upgrade to a E2200 or an E5300 Max
the Person I spoke to at Fry's told me as long ans the Bus speed is the same and the Socket is the same it should also work. Though I have been trolling non stop through these forums now for a day I see more negative than positive opinions. What I cant understand is how this Motherboard WILL support a Dual Core Pentium D but will not support an Intel Pentium 4 Dual Core E2200. Ive checked and ckecked and ckecked and everything looks the same. This link even says that it will support the Pentium 4's and the Core 2's.
And the Link to the HP tech specs above thats posted says it will run a Pentium D 900 series. those ran at 3.0Ghzx2 from what I have heard, so whats the difference?? The E2200 runs at the same bus speed,800Mhz same socket just slightly slower than the Pentium D dual cores. All this is very confusing and frustrating.