My computer started to freeze at irregular times for 3 weeks now.

Please note that this question change with each things that i try. (For additional details)

What happens

• My computer freezes, the video stops. (No graphic glitches, it just stops)
• Sound keeps playing up to some time (Usually 10-30 seconds) then stops playing.
• Sometimes, randomly, the screen on my G-15 keyboard flickers and I see caracters not at the right places. Usually happens for about 1-2 seconds and a bit before my computer freezes.
• I have to keep the power button pressed for 4 seconds to shut my computer down.
• I still hear my hard drives and fans working.
• Sometimes it works with no problems for a full day, some other times it just keeps freezing each time I restart my computer and I have to leave it for the rest of the day.
• Sometimes my mouse freezes for a fraction of a second (Like 0.01 to 0.2 seconds) quite randomly, usually before it freezes.
• No errors spotted by the "Action center" unlike when I had problems with my last video card on this system (Driver errors).
• My G-15 LCD screen also freezes.
• Sometimes my G-15 LCD screen flickers and caracters gets caried around temporary under heavy load.
• Now, most of the times, the BIOS hard disks boot order gets reversed for some reason and I have to put it to the right one and save each times I boot. (Might be unrelated, not sure, but it first started yesterday)
• Sometimes the BIOS doesn't detect my 750GB hard drive plugged in SATA1.

What I did so far

• I have had similar problems in the past and I had changed my hard drive (It was faulty), so I tested my software RAID-0 array and it was faulty so I changed it. (I reinstalled Windows 7 with this part). I also tested with unplugging my secondary hard drive.
• My CPU was running at about 100 degree Celsius, I removed the dust between the fans and the heatsink and it's now between 45-55.
• I ran a CPU stress-test and it didn't freeze during the tests (using Prime95 on all cores)
• Ran a memory test (using memtest86+) for a single pass and there were no errors.
• Ran a GPU stress test with ati-tools and furmark and it didn't freeze during the tests. (No artefacts either)
• I had troubles with my graphic card when I got it, but I think that it got fixed with a driver update.
• I checked the voltages in my BIOS setup and they all seemed ok (±0.2 I think).
• I have ran on the computer without problems with Fedora 15 on an external hard drive (Appart that it couldn't load Gnome 3 and was reverting to Gnome 2, didn't want to install drivers since I use it on multiple computers) I used it to backup my files from the raid array to my 1TB hard drive for the reinstallation of Windows. (So the crashes only happenned on Windows) [The external hard drive is plugged directly on a SATA port]
• I contacted EVGA (My graphic card vendor) and pointed them on this question, I'm looking for an answer.
• Ran sensors on Fedora 15 and got this output: http://pastebin.com/0BHJnAvu
• Ran 6 short different CPU stress test on Fedora 15 (Haven't found any complete stress testers for Linux) and it didn't crash.
• Changed the thermal paste to some Artic Silver 5 for my CPU and stress tested the CPU, temperature was at 50 idle, then 64 highest and slowly went down to 62 during the test.
• Ran some stress testing with a temporary graphic card and it went ok.
• Ran furmark stress test with my original graphic card and it freezed again. GPU had a temp of 74C, a CPU temp of 58C and a mobo temp of 40C or 45C (Dunno which one it is from SpeedFan).
• Ran a furmark stress test and a CPU stress test at the same time, results: http://pastebin.com/2t6PLpdJ
• I have been using my computer without stressing it for about 2 hours now and no crashes yet. I also have disabled the AMD Cool'n'quiet function on the BIOS for a more regular power to the CPU. When I ran Furmark without C'n'q my computer didn't freeze but I had a "Driver Kernel Error" that have recovered (And Furmark crashed) all that while running a CPU stress test. The computer eventually frozed without me being at it, but this time my screen just went on sleep and I couldn't wake it.
• Using the stability tester in nTune my computer freezed again (In the same manner as before). I notived that Speedfan gives me a -12V of -16.97V and a -5V of -8.78V. I wonder if these numbers are reliable and if they are good or bad.
• I have swapped my G-15 with another basic USB keyboard (HP) and I have ran furmark for about 10 minutes with a CPU stability test running each 60 seconds for 30 seconds and my computer haven't crashed yet.
• Ran some more extended tests without my G-15 and it freezed like it usually do.
• Removed the nForce Hard disk controler.
• Disabled command queuing in the NVIDIA nForce SATA Controller for both port 0 and port 1 (Errors from the logs)
• Used CPUID HwMonitor, here are the voltages: http://pastebin.com/dfM7p4jV
• Changed some configurations in the motherboard BIOS: Disabled PEG Link Mode, Changed AI Tuning to Standard, Disabled the 1394 Controller, Disabled HD Audio, Disabled JMicron RAID controller and Disabled SATA Raid.

When it happens

• When I play video games (Mostly)
• When I play flash games (Second most)
• When I'm looking at my desktop background (It rarely happens when I have a window open, but it does, sometimes)
• When my Graphic card and my CPU are stressed.
• Sometimes when my Graphic card is stressed.
• Never happenned while stressing only the CPU. Sometimes when my CPU is stressed.

Specs

• Windows Seven x64 Home Premium
• Motherboard: M2N-SLI Deluxe
• CPU: AMD Phenom 9950 x2 @ 2.6GHz
• Memory: Kingston 4x2GB Dual Channel (Pretty basic memory sticks)
• Hard drives: Was 2x250GB (Western digital caviar) in raid-0 + 1TB (WD caviar black), I replaced the raid array with a 750GB (WD caviar black) [Yes I removed the array from the raid configurations]
• 750W Power supply
• No overcloking. Ever.
• There have been some power-downs like 4-5 weeks ago, but the problem didn't start immediately after. (I wasn't home, so my computer got shut-down)
• Event logs (Warnings, errors and critical errors) for the last 24 hours: http://pastebin.com/Bvvk31T7

My current to-try list

• Reinstall the drivers and software 1 by 1 and do extensive stress testing between each.
• Update the BIOS firmware to the most recent stable one.
• Change my motherboard.

Status updates
Keeping only the last 3

• (28/06 04pm) More stress testing and still pass the tests.
• (28/06 03pm) Been stress testing for 10 minute straight now and 5 minutes with both CPU and GPU being stressed at the same time.
• (28/06 03pm) Stress-testing right now, so far no problems.

A little hope
Tests with Furmark and Prime95.

• Testing Windows bare-bone: 30 Minutes stress, no freeze.
• Installing an Anti-virus and some software, restarting computer.
• Testing with Anti-virus and some software (No drivers installed): 30 Minutes stress, no freeze.
• Installing audio drivers, restarting computer.
• Testing with the audio drivers: 30 Minutes stress, no freeze.
• Installing the latest graphic drivers from EVGA's website (without 3d vision since I don't use it), restarting computer.
• Testing with the graphic drivers: 30 Minutes stress, no freeze.
• Configuring Windows to my liking and installing more softwares.

In this situation, how can I successfully pin-point the current hardware problem? (If it's a hardware problem) Because I don't really have the budget to just forget and replace everything. I also don't really have hardware to test-replace current hardware.