New Computer Fails to Boot

[hockeyplayah]

I took a p6120f hp pavilion computer, and added GTS 250 graphics card (GIGABYTE GV-N250OC-1GI Rev 2.0 GeForce GTS 250 1GB 256-bit GDDR3) as well as this 550w power supply (Rosewill RP550-2 550W ATX12V v2.01 Power Supply)

The computer worked at first, and ran fine for over 2 hours, then I left, with my computer on standby, came back, and tried to wake it up, but it wouldn't respond. So I powered it down, and attempted a reboot, but the only thing the computer would do is boot for a second, and then shutdown and try it again. This process continues repeating until I either shut the power supply off, or unplug it.

I tried to isolate the power supply from the graphics card, but even when the power supply is hooked up to the motherboard alone, it continues to attempt rebooting.

The power supply and graphics card are brand new. Any help or suggestions on how I might fix this problem would be incredibly appreciated.

 

[Whyfly??]

Strange as it seems, this could be because of your CPU overheating.
Check to make sure you didn't knock the heatsink off or nudge it to the side.

 

[hockeyplayah]

I'll go check, however, I don't think it would be, because the first thing I checked was to see if the components were hot.

*edit*

Yea, it's not the heat sink. It doesn't seem to be easily moved, and the most I could have done while putting the units in would be to have tapped it.

How possible would it be for the PSU to be fried?

 

[Whyfly??]

I'll go check, however, I don't think it would be, because the first thing I checked was to see if the components were hot.

*edit*

Yea, it's not the heat sink. It doesn't seem to be easily moved, and the most I could have done while putting the units in would be to have tapped it.

How possible would it be for the PSU to be fried?

It's pretty possible, try taking out the card and using the old PSU. Then we can start diagnosis if it works with the old PSU.

 

[hockeyplayah]

It's not the psu. I tried plugging the old one in, and the computer continued doing the same thing. So I imagine it can't be anything other than the motherboard. Is it possible it somehow fried itself when the computer went into standby? Or is there something else it could be?

*edit*

Also checked each stick of RAM. Switching them out one by one did nothing to help the computer boot.

 

[ringtemek]

It's not the psu. I tried plugging the old one in, and the computer continued doing the same thing. So I imagine it can't be anything other than the motherboard. Is it possible it somehow fried itself when the computer went into standby? Or is there something else it could be?

*edit*

Also checked each stick of RAM. Switching them out one by one did nothing to help the computer boot.

I think it's the motherboard

 

[hockeyplayah]

So what are the options if it's the motherboard? Just by a new one?

And how hard is it to take a motherboard out and replace it?

 

[Whyfly??]

Not very hard. Take off the heatsink, and any add-on cards. Take a photo so you know where to plug in everything. Then just simply unscrew the screws and just reverse the process for the new motherboard.

 

[hockeyplayah]

If the motherboard is store bought, there shouldn't be any add-on cards other than the RAM correct? And how do you take heatsink and processor off, are they screwed down?

 

[Whyfly??]

If the motherboard is store bought, there shouldn't be any add-on cards other than the RAM correct? And how do you take heatsink and processor off, are they screwed down?

Heatsink usually is either screwed down, or just has some clamp that you have to release. Processor you just pull this little lever and it pops off.
You don't have to take the RAM off, only heavy objects that could possibly get in the way of taking off the board. Then once the board is out then take the RAM off. Then put the processor on the new board, put the heatsink over it (Reapply thermal paste if you want or need) Put RAM on. Put it in and screw it in, then put in all graphics cards and peripherals. Look at the picture to know what to plug in and where (It won't be exactly the same but it will give you a good starting point) And just plug in all wires and you should be good to go