That something is amiss. It could be that ethernet card which you could unplug for a test. But the most common issue I find with GIFTED PCs is that the RAM is gone. Did you check that the RAM sticks were still installed and while inside gently push all cards home?
A friend in TV production gave me an HP Pavilion tower w/keypad which he used at his home. It had Vista, was fully integrated and was used for sports videos. He said it crashed often due to the size of the videos so he gave away.
He didn't tell me about this if he knew, but right off the bat when powered up the system makes a beeping noise. It lasts about 15 seconds then stops then begins again.
I read some troubleshooting tips on the HP site online and it indicated that it could possibly be an error in how the ethernet card was installed.
My son is knowledgeable regarding system issues and was able to remove Vista and load XP, but once it was complete the beeping continued when its booted up. He doesn't have the time to continue to help me unfortunately.
I have very little money and wish to either utilize or sell this system as it appears to be a very nice set up.
I greatly appreciate any feedback!