I do not think this is a software problem.
The most frequent software cause of your problem is a corrupted video
driver, which is easy to download and reinstall.
If you listed your video card I missed it. If you are using multiple video
cards, ATI or Nvidia, a problematic configuration may be causing your
issues. Take the second one out and see what happens.
I suspect problems with your power supply more than anything else. The specs
of your machine otherwise are very good and unless you are an ultimate 3d
gamer you will not see any usable speed increase with i7 hardware.
You can download software to test the hard drive and your RAM. In my
experience dying hard drives and defective RAM are rapidly detected by
software tests.
As the problem could be your hard drive I would back it up now while you
still can.
If you are unable to troubleshoot hardware issues, which appears to be the
case, use a repair service.