It's only been like a day and for some reason the computer will randomly freeze completely. Nothing will work(mouse crtl+alt+dlt). It's already happened twice

I built this PC using this vid here

PNY XLR8 DDR3 8GB (2x4GB) 1600MHz (PC3-12800) CAS 9 1.65V PC Memory Desktop Kit (MD8192KD3-1600-X9)

CPU: AMD FD6300WMHKBOX FX-6300 6-Core Processor Black Edition
Seagate 1TB Desktop HDD SATA 6Gb/s 64MB Cache 3.5-Inch Internal Bare Drive (ST1000DM003)
BitFenix Computer Case BFC-COM-100-KKXS1-RP
Sapphire Radeon R9 270 2GB GDDR5 DVI-I/DVI-D/HDMI/DP Dual-X with Boost and OC Version PCI-Express Graphics Cards 11220-00-20G
Gigabyte ATX Socket AM3+ AMD 970 Chipset 2000MHz DDR3 SATA III 6Gbps Ready AMD 9 Series FX Motherboards GA-970A-D3P
PS: EVGA 500 B1 80+ BRONZE, 500W 3 Year Warranty Power Supply 100-B1-0500-KR
Optical drive: Lite On IHAS124-14 Black SATA 24x DVD DVDRW Bulk without Software (Lite On IHAS124-14)

I end up having to press the restart button on the case.

Things i've tried:

-Checked hard drive, no errors
-checked memory using windows 8 memory diagnostic nothing came up
-checked the hard drive and nothing came up
-I have done a virus scan and nothing came up
-I did cmd sfc scannow and nothing came up
-As far as I can tell all drivers are up to date.

-I have power options to "High performance" which I've noticed makes some fan in the unit louder
-I broke on of the clips to the memory slots. Would that have any effect?
-I have windows 8.1 64 bit but for some reason it's saying that I still need to activate it even though everything else works fine
-I'm worried it might be a heat issue,but i used speccy and here are the results as I type this with the game Warframe in the background

CPU 51C (sometimes jumps to 61)
Motherboard 43C
Graphics 58C
Storage 40C

Which is apparently fine, but the case is still very hot to the touch enough to worry me....a lot

This is all making me regret making a PC instead of just buying a pre built one. I googled searched this and this seems to happen a lot a lot of the times the power supply or memory seem to be the problem.

I didn't want to have to resort to memtest because I found it too tedious.