Hi, I just built another computer because i needed a new one because my old one ws slow. I bought an i5-3570k (http://www.newegg.com/Product/Product.aspx?Item=N82E16819116504), an ASRock Z77 Pro3 (http://www.newegg.com/Product/Product.aspx?Item=N82E16813157297), 2 x Samsung 4GB DDR3 1600 RAM (http://www.newegg.com/Product/Product.aspx?Item=N82E16820147094), 320GB Seagatte SATA hard drive. I did not get a graphics card becuase i didn't hae the money so i am using integrated graphics for now.
Originally i had bought 8GB of the Corsair Vengance ram and a different hard drive, but i then returned those because i thought that was the reason my computer was freezing. Once i got the new ram and hard drive i reinstalled windows and it still was freezing. It didn't freeze immediately it only froze after i had been using it for about an hour or so. Once it froze nothing worked i tried ctrl+alt+del but that didn't work. the only was to get it to work was the unplug the power and plug it back in. After that it would work for another hour or so then freeze again.
Inland ATX ILG-500R2 500W Gold Series, Single 12V Rail. I don't know if it is the psu becuase after it freezes it stays on until i manually turn it off. But it could be, I have no idea what is causing it.
So hitting the reset switch or holding the power switch doesn't work after freezing? If that is the case then the cause seems to be pointing to either the motherboard or the PSU. Also I am not familiar with inland PSUs,but $20 for 500W seems a little iffy to me.
The PSU... never heard of that brand before. Kinda fishy.
But I had a had problem of freezing and random restarts. I had my RAM returned since I thought that was the problem after several tests, but like you, it still froze when I got my new RAM.
What I did was change the RAM voltage be incriments of 0.05v in the BIOS and test my systems stability with Prime95. My RAM were originally marketted at 1.25v but when I raised it to 1.3v, everything was stable up to this day. Usually it would just freeze or crash after 2mins running Prime95, now I test it like a day with it, no prob.
Try it out, and if it doesn't, then it might indeed be your Mobo or PSU.
Borrow a PSU from a friend and check if same stuff happens on his PSU also. If not - you have the culprit. If it will be the PSU try to buy an OCZ one since they should be cheap and with good quality.