I am trying to do the same thing but running into a lot of problems I was not expecting.
1) I have upgraded to a Q8400 Quad core and now I get the 1801-Microcode Update Error and the CPU Fan stays at 100%. Sounds like a hair dryer.
2) I have loading Windows 7 pro 32bit and the audio drivers it auto loads do not work. I have tried other IDT drivers for Windows 7 from the DC5800 minitower configuration and they don't work. saying my hardware doesn't match.
I consider myself pretty good at PC building but this has me stumped.
HP dc5800 SFF
Q8400 Quad Core CPU
1GB x 4 DDR2 800mhz
Nvidia GT 430 LP Video Card
1TB Seagate Hard Drive