At least it's a very weird mystery for me, I hope not for all of you. Not sure if this is the best forum, so I posted this in graphics cards too. It's a bit of a long story, so please bare with me.
Last week my computer had a hiccup. While I was gaming I got some error message and the game shut down. I didn't think much of it as it was the same sort of error I've had a hundred times before. But then I noticed a little yellow triangle in the system tray (Vista by the way). Looked it up here to be told that means some kind of hardware malfunction. Followed the advice I read here to check device manager and look for the triangle, but found nothing. Still wasn't too worried about it though, I assumed it would disappear when I restarted.
So the next time I started up the computer, it beeped horribly, and nothing at all came up on the monitor. The screen said "no display" and switched itself to standby mode. After a long series of trial and error experiments unplugging various components, I got beeping sounds every time I started up, although they did vary a little depending on what hardware was plugged in.
What's really perplexing is that with the speakers plugged in, I can hear windows starting up just fine. It even shuts down if I press the power button once. I think the mouse was working OK too as it was lit up, but the keyboard was not, and pressing Alt-F4 and then the doown arrow and then enter didn't get the computer to shut down, so I don't think the keyboard was being registered.
So I took the computer to a local repair place, thinking it must be the graphics card but not having any spare equipment to test the theory. So in the shop we replace the graphics card, and still no display. Replace the RAM, no luck. So the guy there tells me it must be the motherboard, or the PCI Express slot in the motherboard. We figure it can't be the harddrive or CPU or RAM since the computer does seem to boot OK (based on the sound). This is further supported by the serious beeping noises. I ask if he's sure, because he doesn't seem to be, and this will mean investing in a new board, but he says he is. So I go out and I order a new mobo.
After a long week with no computer, it arrives and I install it. When I try to start it up, the same beeping and no graphical display. I plug the speakers in and sure enough, windows is starting up.
So, someone please tell me, what the hell could this be? He replaced the RAM and graphics card and that didn't fix it. I have a whole new mobo and still no go. And Windows starts up and shuts down! I'm no computer wiz but this has me totally stumped. We've had bad experiences with this repair place before, so I'm loathe to take it back there, and I'm not sure if there's another one in town. Seems it must be a hardware failure, but in which piece?
I have an MSI Neo-F (old mobo) and now an MSI K9A2 CF-F (new mobo), ASUS x1950Pro GPU, 2 gigs of PC2 6400 Corsair RAM, Athlon X2 4600 CPU, Tripower powersource (can't remember the details of this off the top of my head, can find them if someone thinks it matters). Running 32-bit Vista home premium.
My only guess - power supply went partially tits up and is unable to provide enough juice for the gfx card. Check the power cable that plugs into the card itself, especially at the plug. If the guy at the repair shop is willing to help ask him to try different PSU.
The graphics card he used was one that didn't require an extra power plug (i.e. no direct connection to the power supply). Plus, that wouldn't explain the motherboard beeping even with the card disconnected, would it?
Motherboard WILL beep when you pull the gfx card out, as thats how it reports video error, but then the PC should boot and load the system normally(indicated by working hdd and widows sounds) which is happening in your case. Because you tried different gfx in old mobo and also a new mobo, my bet is still on PSU(or part of its circuitry) being at fault, i cant explain why but it seems somewhat possible to me. Of course i might be totally wrong but if you can, try a different PSU. Go to that repair shop and tell the guy "Listen you a-hole, you made me buy a new mobo which seems to have been unnecessary, now let me try some good PSU"
OK, that's good to know. The PSU is certainly looking the most likely culprit at the moment, unfortunately I don't have any replacement or means of testing it, so unless someone knows of some ingenius way I can test it I probably will have to go back to the shop, which will be a pain.