Random BSOD - Error 0x0000000a And 0x00000050?

Been having random BSOD for the past week or so. Started on Sunday (11-27-11),where I had come back to my machine and it had been restarted... after logging in, find out that it was a BSOD. I then proceded to have 3 different BSOD events on Monday, which led me to perform a memtest on Tuesday morning to see if my memory was bad. After 2 full passes (I know, not a full 8), it didn't seem to be that, so I went ahead and did a System Restore from a backup from roughly 2 weeks prior. This led to solid performance for the next week, until this morning (Monday, 12-5-11) when I had another. All BSOD events seemed to occur at random times, so I can't say they were triggered by a specific event to the best of my knowledge.

I had performed the BSOD dump collection and Performance Monitor Report on last monday as well as doing the BSOD dump collection today. Regretfully, I cannot get the Performance Monitor to stop running today, so hopefully just the dump collection will be enough.As for my computer components:- HP Elite 7000 MT machine- Windows 7 Ultimate x64- Not the version originally installed on system- Hardware is a little over a year and a half old- 64-bit OS (originally had x86) wasinstalled 13 months ago.- Only non-stock hardware would be an added harddrive (just a backup drive, no OS on it), and I added 4GB more RAM (alongside the original 4GB) back in January.