Trying to diagnose a problem?

Here's some background information. I built a sweet computer for a friend of mine. I put it together, loaded everything on it, Sweet computer! After a month or so i get this call saying "my computer wont start". The guy's a noob and throws me for a loop, "what do you mean it wont start?" "i turn it on and i see the motherboard logo, after that i get a flashing _ in the top corner." "Did you do anything to it?" I ask. "I turned it on" he replied.

Well jeeze, there aint much i can do over the phone so i head to his house. After playing with BIOS setting i tell him i have no idea whats wrong. I sugjest that reinstalling windows might be an easy way to fix it though he'll loose all his music and crap. This is where it starts to get intresting. The mobo driver cd wont let me create a raid disk, says the drives to big and gives me some funky error. Damn! Ok, I remove the raid array and try installing windows to a single disk. Problem, windows freezes at the user agreement page. After a few tries with no luck i told him i thought his mobo might be fried. I tell him to take it to a computer store just to confirm its the mobo so he can RMA it back to NCIX. He procrastinates for 2 weeks before bringing it over to my house so i can take it to the store and explain what i think is happening.

Before i took it in to get looked at, I sent a msg to NCIX explaining what was happening and that i might need to RMA a defective mobo. They msg me back asking me to test the ram first. So i remove the ram, mix up the sticks and put em back in. Next day i wanted to power it up and start testing the ram stick by stick. Well, i had left the windows cd in the tray from the last time i tried to fiddle with it. It starts loading the windows kernel ect,ect. Wait a minute, it actually shows me the user agreement this time. I know the raid aray was deleted but its working. Ok, lets see how far she'll go. It installs windows fine, ok. All drivers and everything on my computer that i can give him installs fine. Only problem i can see is that his second hard drive doesnt show up in my computer. I tell him "well its working, no raid though" He complained a bit about not having the performance of raid but agrees to take it home how it is.

About an hour after he leaves, i get a call. "I pluged it in,turned it on and it wont work"

This is where im at now, 1 day after the previous 2 paragraphs. Any thoughts before he spends a bunch of money at the computer store? I've exhausted everything i can think of.

His system specs are as fallows:
CPU: C2D 2.4Ghz 1333FSB (cpu code number eludes me)
mobo: Asus Striker Extreme
Ram: 4x 1Gb Kingston HyperX 6400
GFX: BFG 8800GTS
Drives: 2x 500GB WD sata2 drives with 16mb cache
OS: WinXp Home sp2 cd

PS, this is a duplicate thread. It was sugjested that i move it here. Could a mod please delete the original in "mobo mojo".

After buildin a few pcs from newbies and getting the same classic 'it wont work' call when you know just coss you built it youve gota sort it I can apprieciate your issues.
Only thing I can think of is Har Drives have you run a diagnostic on them? Could be a power spike in psu had trashed 1 drive so it doesnt show up at all and the other one so it works a bit but isnt stable. If everything works and your not gettin memory exception errors while doing install. Ill try to think of anthing else good luck.

I would make a bootable diagnostics disc with something like eurosoft pc check, and run checks on everything, mobo, ram, hdds ect and make sure it all comes back ok. that way at least you will know if its faulty hardware.

remove the hard drives, or disconnect them completely. install a new hard drive, or one of your own and try to get it to recognize that.
Provided the hard drives are your only issue at the moment. Is it SP2 for windows? Cause i know some mobos have issue with older pre sp2 versions of xp and proper raid functions within windows. Also check to ensure your jumpers on the hard drives are correct and that they both load and are recognized in bios.

Thats all I can think of for non damaged but non working hard drives at the moment.

Well Thanks for all the replies guys. We took the mobo back to NCIX and after a 20 minute interagation from the guy behind the counter, we were given a new mobo. Got back to buddies place and pluged it in. Everything seems to be working as it should.

well thats good to hear, strange situation none the less.