Help Needed: Computer showing only blank screen

[Ictoo]

Yesterday i got my computer out and started to clean all the dust out, it needed a spring clean.

The only things i took out to clean was the graphics card and the CPU, the paste was very dry so i cleaned it and added some new paste.

I put everything back together and now the computer when it starts, after 5-6 seconds restarts it self and then and it just showing a blank screen.

I've tried a different graphics card and still a blank screen, i think my mother board does not have a built in speaker so i'm not hearing an beeps and i think it's not even posting. I think its the CPU from what i've read. but could anyone give me an idea of what it could be so i could at least test a few more things before i up and spend £140+

Asus P67 Sabertooth Intel P67 (Socket 1155) DDR3 Motherboard
Gigabyte GeForce GTX 570 1280MB GDDR5 PCI-Express Graphics Card
Intel Core i5-2500K 3.30GHz (Sandybridge) Socket LGA1155 Processor
Kingston HyperX Genesis Grey 4GB (2x2GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (KHX1600C9D3X2K2/4GX) x4

Current hardware.

 

[Ictoo]

Also there is a red light constantly on by the ram/memok button trying differ t ram in now and still same thing.

Press memok button it flashes restarts the computer then the light just goes back to red.

 

[Ictoo]

Trying that right now, in A slots and B slots. Getting nothing so far.

 

[Ictoo]

Just looked under the CPU again and it looks like one of the pins has bent, looks like I might need a new mothers board- does any one recommend a new one within the price range of £100?

 

[Ictoo]

Thanks for all your help, it's all sorted now! wazza I did what you said gave up half a dozen times but finally it seemed to be back in place tried it and worked! It was just that one pin, missed it on my first run down.

Thanks for all advice and quick responses.