OK so I have been working on this desktop PC for a little while now. Its an HP Compaq Business dc5000 Small Form Factor PC. And It was wiped out by a rootkit. I Replaced the hard drive because it was old and causing other problems. I had assistance from MDL on reflashing the BIOS from 1.00 to 1.43 and I flashed the Intel chipset update. IT had an Intel Pentium4 2.80GHz/1M/800MHz FSB BUT it has 400MHz memory modules installed. The system worked fine before the rootkit but now it WILL NOT work with that CPU installed and CPU cache enabled, I pulled that CPU out and replaced it with a 2.40GHz Intel Celeron D/128/400 for the time being until I figure out why it wont take the Pentium4. It has the Socket PGA478. I'm just not understanding how this worked to begin with??? Don't make sense. It works fine with the Celeron D but I need the Pentium back in it as its not my computer. Any suggestions???