Windows 7 - Restarting, again, and again.

My sister's boyfriend brought over his computer and an extra case, the task, move his computer components into the other case since the other case had working Hard Drive mounts.

So we extract everything from the old case and clean off the layers of dust and condensed dust bunnies from the fan areas. We used compressed air canisters bought from the local computer shop. I used the canister to blow air out of the heatsink, fans, chipset heatsink, the graphics card, and the PSU.
I also put Arctic Silver 5 on the CPU and Chipset heatsinks.

We then put everything inside the "new" case but everything was a tight fit due to the sheer size of the motherboard and especially the graphics card.

After hooking up everything we turned it on. . .Then it shut itself off, then turned itself on and stayed on, but nothing showed-up on the screen, both of us directing attention to the GFX card.

But after tinkering and trying many techniques, including a BIOS reset, disconnect the hard drives, then take out the GFX card, but the issue persists. The computer turns on and then shuts off, again, and, again, and again, stuck in this loop. I'm suspicious of the issue being power related, but there can also be a different hardware issue.

I want you to all post any and all solutions possible, he is staying the night for 4 days and we are scratching our heads over this, we will read and follow any advice and possible solutions given so please post anything you would suspect to cause this continuous restart loop.

Computer specs:
OS: Windows 7 and Linux Dual-boot
Processor: Intel i7 920 using stock fan and heatsink.
Motherboard: Intel DX58SO (this thing is HUGE)
RAM: 6GB DDR3 1600
Hard Drive(s):
x1 1TB SATA
x1 500GB SATA
x1 200GB SATA (boot drive)
Graphics: Nvidia GeForce EVGA 9800GTX 512MB (long card)
Power: 500W unit

Again, please post any possible fixes and we will attempt them next time we look at this thread.
Thank you.

Please double check all connections from the power supply to the motherboard, hard drives, graphics cards, CD drives, floppy, etc etc etc. After this, ensure that the processor is seated properly, as is the RAM, and remove all but one stick of ram and attempt the boot (try with all sticks of RAM if the issue persists, to rule this out).

The DX58SO is an ATX standard motherboard. Are you trying to fit it into a case that was designed for micro-ATX? I suspect this from the "tight fit" and "huge" comments.

If this is the case, then you want to carefully examine the mounts on the case and the corresponding mounts on the motherboard. They will be different on a micro-ATX case. If you have a mount on the case that is not aligned with a mount hole on the MB that can cause a short circuit which could explain your symptoms.

If the video card is not seated properly - not all the way in - because of obstructions this will also cause that symptom, as will any other component not connected properly as LiquidSnak said.

To test for power issues disconnect all but essential components: CPU, RAM, Video, and only the boot hard drive, keyboard & mouse.

It would also be helpful for us to know the configuration of the old box vs the configuration of the new box to see if you have mixed-and-matched parts.

Ina addition to the great advice above, double check the P4 connector from the power supply, and make sure that it is securely attached to the motherboard in the CPU power plug. That will definitely cause a shutdown.

@TVeblen: The "new" case may be an ATX case for the reason that I saw only ATX brands stamped inside, when he wakes up we are going to switch everything back into the old case.

If it still does the restarting when connected in the old case then I will try all of your other fixes.

UPDATE: Okay, it is running again after putting it in it's revious case, thank you all for your suggestions and help!

This very issue has been caused by over-tightening of the CPU cooler.

By how the i7's heatsink is set up, it's not possible. . .

right, you said the stock cooler.

Glad you got it running. Next time try a bigger case, it may work better. Get a HAF X, you can park your truck in it.

And if it's watercooled, you can park a battleship.

Glad you got it fixed PwnFrnzy.