I had to upgrade my PC as well, starting from scratch, bought two mobos, one is ECS with nVidia integrated, having a hard go of it so I went also with G31 chipset MSI brand. That one has a 3100 series Intel Express chipset tied to the NorthBridge.
Well, right now CPU wise I have a single core HT that shows up as dual cores in Device Manager, it is 3.2Ghz, best I could do at the time. I can run Quad and Core2Duo, but how about a Pentium D on a budget? Around 2.8Ghz? Anyone try that out??