[AFCop]

I posted this in general because it involves multiple hardware elements...

I went to install a second graphics card (NVIDIA 260 GTX) and when I hit the power button, it flashed on for a second and powered off immediately. Now I can get it to even turn on.

I didn't smell or see any smoke.

I removed the second card and it still won't turn on.

I tried placing the first card into every available slot and no go.

I put my old card (NVIDIA 9600 GT) in every available slot and no go.

I unplugged and reattached all cables...still nothing.

I cycled my PSU and still nothing.

When I turn on the PSU, it looks like some LEDs (a power and reset switch near the bottom of the board) on the mobo are lit, the sound card is lit (the mobo comes with its own), but it just won't turn on.

I think I may have connected the new card to the wrong slots on the back of my PSU. My cards take two 6-pin PCI-E cables. I had two open 6-pin slots on my PSU. But after closer inspection, I saw that those two slots were actually labelled "4-pin floppy" or something like that. Two of the PCI-E slots were being used for the first card and two other 6-pin slots were being used for my optical and hard drives (they were labeled E-SATA I think). The sole 8-pin slot on the back of the PSU was hooked up to my mobo, the 24-pin cable was connected to my mobo, and I still had two 8-pin cables coming straight from my PSU, but had no 8 to 6-pin converters, so I didn’t use them. They weren't connected to anything. It leads me to believe that there was a voltage difference and I fried something when I used those "floppy" 6-pin slots on the PSU to connect to my video card.

My PSU is a Thermaltake 850W Toughpower and my mobo is an ASUS Striker II Formula.

Any ideas, help, suggestions?

[Hybr!d]

Sounds to me like you blew the PSU.

Based on the symptoms you describe.

Non powering-on PCs are PSU issues or mobo, but the PSU is the first port of call to look at.

[Carbon]

If both cards.(I assume both GTX 260s) were on the same rail, you may have exceeded the 18A capacity of that rail. Buy a single-rail PSU next time...

[AFCop]

What do you mean by same rail?

[Carbon]

http://en.wikipedia.org/wiki/Power_s...e_.2B12V_Rails

Wiki explains it better than I do. Connecting multiple graphics cards in series to one rail can overload that rail, on most power supplies this will simply force the unit to shut down but a failure in limit circuitry could blow the whole thing. This is why many multiple-rail PSU manufacturers clearly label each rail so that each graphics card can have its own source of current.

[AFCop]

So, if this were the case, is the damage limited to the PSU, or could it also have affected the mobo and graphics cards, or even the CPU?

I think what happened was I had one card using two 12V plugs, both SATA plugs were being used, the 8-pin plug and the 24-pin cable were connected to my mobo as well. The only things that wasn't connected as far as the PSU is concerned are two 8-pin, 12V cables and 2 6-pin 3.3V or 5V plugs (I dont't know which). I mistakenly hooked the PCI-E cables to the lower voltage plugs in the back of the PSU and connected them to the graphics card.

So, am I totally screwed? I can deal with replacing the PSU fairly easily, but if I have to replace the mobo, cards and PSU...that's a very tall order.

I'm trying to figure out where the damage is contained before started to replace things.

[Carbon]

I would replace the PSU with a quality single-rail one and try it out. It's likely to cost you very little, and is your best shot. I recommend the Corsair 650W or one of the 600W+ ones from PC Power and Cooling, whatever is cheaper in your area - these will have enough 6 pin connectors natively as well. They won't be modular though - you'd have to go with the 1000W Corsair, which is really not worth it.

[AFCop]

Interestingly enough...the computer repair shop I took my PC to said it was the mobo that was fried. The tested the PSU and graphics cards and they both worked.

So now my next question is:

When I get a replacement mobo, can I just install it and will it work normally? Or do I need to be aware of anything else like reinstalling the OS, drivers, messing with the BIOS again, etc?

[Carbon]

Weird. Motherboard failure is pretty rare. Anyway..

Yeah, you can. If it's a direct replacement, Windows shouldn't whine - if it's different, you may need to call MS and explain so they can reactivate your copy. Same deal with drivers - if it's a different one, you'll need to get rid of all the motherboard drivers from the old one.

You may need to set timings and voltage on your RAM as needed in the BIOS, and any overclocking will of course be reset.

[AFCop]

Yes...I will be replacing the mobo with the exact same one. I am using a retail copy of Vista Ultimate (no OEM products). Nothing else is changing. Just the board.

So in other words, I can theoretically plug and play with the new mobo aside from resetting BIOS memory settings and such?