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In a mess :( - PC won't power up after new motherboard, cpu, memory and graphics card installed.

nikez2k4 asked
Medium Priority
Last Modified: 2010-04-25
Hi guys.

I recently updated my motherboard, processor and memory - for the interested:

ASUS P5L-VM 1394
Intel Core 2 Duo E6400 (2.1GHz)
1GB Stick Corsair DDR2 RAM

Formatted the PC and it all worked flawlessly - very smooth, even with the integrated GPU. I then ordered a new graphics card - eVGA NVIDIA 7900 GTX - here is where the problem starts...

I am a little ashamed to admit this - it was a completely stupid thing to do...not to mention costly!

I turned the pc off and pulled the tower out. I opened the side and got on my back armed with my shiny new graphics card. As I started to plug the card in the PC suddenly powers up and then down again, at which point my heart sinks and I realise what I have done...

Dont ask why but I had forgotten to unplug the power from the back of the PSU - I KNOW ITS A ROOKIE MISTAKE!!! - and now I have a lifeless PC... :(:(:(

Anyways, the power button didn't work and I frantically tried to get it up and running again to no avail...so I decided to order a new motherboard which came today. I have just installed it and connected everything up and guess what? Nothing :(:(

Now I am £100 lighter and have absolutely no idea what is wrong with my PC. I thought it had to be the mobo as there was no power going anywhere, it would still start up and freeze if the proc and/or memory were dead right??

So now comes the question... How can i get my PC back up and running cheaply?? What should I start looking at? It is a brand new abit AB9 mobo so I can almost guarantee there is nothing wrong with it. I have a 400W PSU with a 20-pin connector....Could this be a problem? The mobo has a 24-pin connector and the manual says you might not be able to boot with a 20-pin although it will work...

Could the PSU have been damaged? Or am I looking at...*takes deep breath*...a new processor and/or memory stick?

Can anyone help?

Appologies for the long post....thanks guys!

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Top Expert 2012

Don't panic just yet - you need to test it with a different video card that you know works.  You may have damaged the 7900 GTX (panic!), or the Abit motherboard may be no good (I had to go through 3 new Abit motherboards to get one that worked, so I'm not buying Abit anymore).  The RAM also needs to be swapped, since it may have been damaged.


I don't think (touches wood) it's the graphics card....I caught the backplate on the motherboard so that shouldnt have touched the main board of the GPU should it?

I am willing it to be the PSU - there doesnt seem to be power going to any of the USB ports, however it could also be the fact I only have a 20-pin atx connector so maybe its a power thing rather than somehting is faulty.....but then it would have worked with my old motherboard wouldnt it??

I'll test some things out tonight and if the PSU is now a brick then I will have to goto the only place open at night *grits teeth* PC World :(

Top Expert 2012
If you never touched the edge connector of the card to anything, it should be ok.  The PSU should have worked with the old motherboard, so if it doesn't work with it anymore, it's suspect.

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Naaa it was just the backplate that caught a couple of "wires" on the motherboard - so what is the possibility of it being the processor or memory? If I managed to blow them could that comepletely stop the pc from powering up?

Top Expert 2012

Yes it could.  The cpu tends to be fairly isolated from such things, though.  RAM and the motherboard are much more likely to be the points of failure, so you will need to swap them.


Callandor thank you. You have put my mind at rest, at least for a little while.

I have someone testing my PSU as we speak (and yes i DO trust him lol!), so I will let you know what the outcome of that is.

Glad to know that the CPU is at least somewhat protected, its being very new I thought it should have had some kind of protection...

oop - results are in.... My roommate just said my PSU is FUBAR (aparantly that means F**ked Beyond All Recognition) - so I hope that means the PSU absorbed most of the failure hehe - I don't want to spend close to another £100 on a memory upgrade!!

Will get a new PSU tonight and see if that works - if not then, well I guess I'll be back here asking for more help.

Thanks again Callandor!


newer mobo's with a 24 pin atx connector, require the extra 4 pins to pwr the newer cpus.



I managed to sort the problem. There was no problem with my motherboard, cpu or memory, however after replacing the PSU the system booted up nicely and I now have an amazing PC working very smoothly with Vista :)

Thanks everyone!

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