troubleshooting procedures for problem on my computer?

[Sam]

Ok.... So for about maybe 1 1/2 months now I have had to deal with my computer (that I built) freezing/hanging or whatever the technical term is- exactly after 2 hours and I have to force shut down it. Its gotten pretty annoying now because I use my computer for both gaming and school and and my essay (if I wasn't using google drive) would've gotten deleted because I didn't save and the comp froze.

Over the past week ive been trying to rack up information on what could the possibilities be. These are the possible issues my comp could be having:

-virus
-hardrive malfunction (I do get the bluescreen)
-Ram malfunction
-overheating (I doubt this it, but it could be)
-using too much of CPU
-OS problem (I use windows 7 home edition)
-driver issue
-exe/registry problem

These are the problems I think may be on my computer (problem even more or multiple). What happens right after 2 hours is that every application I have open either slows down or just immediately stops. my mouse can keep moving and click on a new application, but it won't open.
Other symptoms I've noticed are sometimes a sort of transparent whitish screen comes when I log in to my OS, but the mouse still moves but it cannot click on anything and I have to force shutdown (recently this hasn't been popping up).

I am techy person, but I'm not much of a troubleshooter so how would proceed to do any sort of troubleshooting? Here are my specs if know them will help.

CPU: Intel 3450
motherboard: Asus P8Z77-V
Ram: 1 stick 8 gigs
graphics card: Nvidia GT 440
Hard drive(s): 1 120 GB SSD (contains the OS) and 1 2TB seagate green HDD
OS: windows 7:
fan: hyper 212 plus