BSOD when computer sits idle

So I'm running an older computer. Started with vista, went to xp, then upgraded to Win 7 64x after the upgrade advisor said everything would be ok. Immediatly I started getting BSOD and after reading many message boards I decided to swap out the ram with new ram. This didn't seem to resolve the issue so I removed 1 stick ( mobo holds 2 ) and things seemed to stabilize until i let the machine idle for 5-10 mins then it would BSOD with mem management errors or irq not equal or less errors. So I upgraded drivers, got all windows updates, tested RAM, tried stripping hardware down to bare minimum, removed anti virus, and like 100 different things. Everything ran fine for like a year with vista and xp and now I can't get anything done. The only time it seems to run fine is if I'm running World of Warcraft or streaming video otherwise the BSOD can and will strike at anytime. I've including some of my most recent dumps. I'm only running 2 gigs at the moment because that is all that's allowed per slot and if I try to put a 2nd stick in it blue screens almost immediately. This made me think maybe the slot was bad but I've tried switching it between slots and different sticks and that doesn't seem to make a difference.

Currently in computer
OS- WIN 7 PRO SP1 x64 free through school
Dual Core intel pentium D 2.8ghz
2gb crucial PC2-5300 DDR2 240 pin DIMM RAM
ATI Radeon HD 5750 video card
Foxconn P4m900-8237A motherboard
Acer X183H
ST3500320AS ATA harddrive

You can use minidumps for analysis..
You can find these in C:\windows\minidump.

Also check out the power supply power points, might be the problem with power supply cable powering graphic card. Check that cable, it might not be working.

I've ran the memtest86+ repeatedly on all the sticks of ram I've been trying to use and they all pass with flying colors although that doesn't mean much because in the month I've been looking into this problem I've seen more then 1 person say the same thing and then buy new ram and have the problem solved. Which I've also tried and tested new ram, Going to try the driver verifier now. I checked that power cord and it seems fine and I know about the minidumps they were attached to my first post because you can't just open and read them you need like windows debugger and the symbols and although I'm pretty computer literate trying to find a way to be able to read them left me with a headache. Anyways I hope this verifer works I'll let you know.

ok so it's been several days with no blue screen which is longer then it's ever gone. I seemed to have 2 different issues which I want to go over fast so this will hopefully help someone else. The biggest issue was when trying to use 4gig or more of ram the system would crash immediately but less then 4gig and it ran ok as long as it didn't sit idle. To fix this I went to run and typed MSCONFIG, then under the BOOT tab I went to advance options and at the top I clicked the processor box and made sure I put 2 in there (for 2 processors) and I clicked the MAX RAM box and entered 4000 in that box. The site I got this information from said to use 4096 which I tried but it kept clearing itself out and the 4000 stayed so I went with that. I applied these settings, exited out and shut down windows, I then put the 2nd stick of ram in and started up and everything ran ok for a about an hour which was way longer then I ever got with 4gigs of ram so I was pretty happy. Finally I uninstalled the ATI Radeon HD version 12.2 drivers and downgraded them to the 9.11 drivers (these seemed to be the ones that got the best review for stability). After that I've had the computer running ever since with no blue screens. Hopefully this helps someone else because I know it gave me quite a few headaches and left me quite miserable for some time.