WinXP won't boot, PLEASE help!

OK here is the scenerio. I built a system for my friend using alot of old parts from my system that I upgraded. I first formatted the HD using the WinXP disk (not quick format) because the HD was new.I installed XP Pro, MB drivers, video drivers, and some programs he wanted. System ran fine no problems, was restarted a few times with no problems during install. Was restarted a few more times after, still with no problems. I took the PC to him last night, he used it for a bit, and went to watch some TV. His daughter got on it, and was playing Spider solitaire, when the screen went black. He came to the PC later and turned it on, everything went fine, until he got to the login screen. He clicked the login, desktop came up, an error came up for maybe a second, and everything went black. He tried again, and said he quickly hit the don't send button and windows started up ok. Don't know if this is relevent, but he started to install microsoft word. When he realized he couldn't find the passkey, required for installation, he cancelled the installation, it went back to desktop, and everything went black again. He tried to restart the PC again, and it runs through the memory check, and lists the drives and all, then goes black. He has tried several times and gets this same result. I had him go into bios, and read off everything and seems to be in order. I say the PC is going black, rather than shutting down, because the case fans are still running. I can't verify what else is running though, as the PC is not here with me. I just need to know what direction to look in.

Here are the specs, and what is new, and what I used from my system, and old parts from his crap box. My system never had any problems running any of these parts, and his just started using them yesterday.

Old parts from my system:
Gigabyte GA-7VAX
AMD Athlon 1800XP+
Elixir DDR2700 512mb ram (single stick)

New parts:
Maxtor 60gb 7200rpm HD
ATI Radeon 7000 64mb 4xAGP video card
Rosewood DVD/CD-R combo drive

Parts from his crap box(HP celeron system):
floppy drive
56k modem
15" HP monitor

If it matters the service packs have not been installed on the PC yet, because he is on dial-up, and we were going to bring it here to get them on cable.

 

well it sounds like a hardware problem, but to be sure you could have him boot into safe mode and see if the system works that way.

 

This may sound stupid, but how do you boot XP to safe mode, if it doesn't prompt you? I have never had a situation where I needed safe mode, but wasn't prompted with the option.

 

http://support.microsoft.com/default.aspx?scid=kb;en-us;315222

 

We tried booting in safe mode, and it still comes up with a black screen. So does that mean that it's a hardware problem? Maybe the video card? Any input or ideas are welcome.

 

Please! Does anyone have an idea? I need to get his PC back up. His daughter uses it for school.

 

I would check:
Monitor
Memory
Powersupply
Graphics card
Check the monitor first, then maybe memory try another stick, graphics card could be bad, try another if possible, I keep basic PCI card on hand for trouble shooting.