But then again, you've changed power supplies, tinkered with the motherboard, etc.. Other than that, if you can't take it back, I'm in agreement with you. The next step would be a motherboard replacement.
Hope this helps.
Hi, I recently bought a new PC which worked fine for a couple of weeks but then one day I went to turn it on and the machine fired up but nothing came up on the monitor. The CPU fan and the power supply fan started spinning and a green light on the motherboard came on but the monitor said it was getting no signal. Then, when I tried to turn it off by holding down the power button on the front of the case it didnt work forcing me to turn it off at the mains. I also noticed there was no power getting to the CD-ROM. (Im running XP, the motherboard is an Asus A8S-X, the processor is an AMD Athlon 3800 and the graphics card is a Radeon 9250). I tried a different monitor and power supply but that didnt work. I also tried re-setting the motherboard and re-seating the graphics card but none of that worked either. I guess the obvious explanation would be a faulty graphics card but the fact that the CD-ROM isnt getting any power and the machine wont turn off when I hold down the power button would suggest a problem with something else, maybe the mobo? Any help would be greatly appreciated. Thanks.