Hm. Don't know too much about changing CPU's in that board, or what he's locked into there. But you might have him look into a better graphics card. The 9500gt's are kind of weak. Maybe check out something like an ATI 5750 or 5770 to get a bit more out of it without breaking the bank. Though I would also be mindful of his power supply as that may need upgrading as well.
Buddy of mine needs to upgrade what he's got to get by for now.
He has Dell XPS 410
Dell Motherboard/ OWG 855
Is there any CPU or anything that will fit this older machine to give it a boost?
Would really appreciate input!
As stated by ohiou_grad a video card upgrade would be the best bet.
The power supply will handle a 5770 without a problem.
As far as cpu's, Conroe and Allendale Core 2 Duo's or Kentsfield Quads upto the Q6700 will work.