Need advice about upgrade path

I've been using a dell sc420 server as my game machine. I had to hack
in my Geforce 8600 GTS because the PCIe was only big enough for a 8x
card. It's worked OK for a while but I did have to change out the
power supply. The P4 connector looked cooked. I borrowed a friends and
it worked fine so I replaced it.

Now it's a 2 years later and it's happened again. But a new power
supply wont work. I guess it's the mobo or the cpu. But I can't tell
which.

It's a 775 so I figured I'd just buy a 775 mobo and test the cpu. If
the CPU don't work I'll just buy a core 2 that fits a 775.


Does that sound like a good course of action? If the CPU on this
computer still works I'd like to use it in a server. Hate to get rid
of a working P4 2.8 1meg cache. Is it worth going thru all this
trouble or should I just look for a new mobo/CPU combo?