Ouch! Well you didn't need those 4 weeks of your life anyway, right?:sarc:
So back in the lab.....
You need to try and zero in on what component or driver is responsible for the freezes. I suggest a methodical approach.
The computer only needs the case (switches), power supply, motherboard, CPU, RAM, Video Card, and HDD to run. I would remove or unplug everything else. During the diagnostics I would leave the side(s) off the case.
Use proper static precautions.
Power Supply: A prime suspect in any freezing/crashing computer. We never got to see what brand and model. You need to have a PS that produces enough amperage to run all the stuff. Do you have another power supply you could switch out to test?
Motherboard: You don't want to go about and make custom BIOS settings changes while doing diagnostics. The computer should run normally at normal (default) settings. Obviously, things like AHCI must be changed, but everything else should remain on BIOS defaults during diagnostics. If and when everything seems to be running well, then start to make custom BIOS changes, one at a time, testing after each change. If the BIOS default sets your RAM to 1066MHz - leave it!
In general, during diagnostics, only make one change at a time. Doing two things at once just muddies the water.
RAM: Try running with just one stick. Then try the other stick alone. You might bite the bullet and try new RAM - It's a good idea to buy something right off the QVL list when you suspect motherboard/RAM issues.
Video Card: Try it in another slot if you have one (you must removing it from Device Manager first before doing this).
HDD: Check all your connections, try another SATA cable, use a different SATA power connector.
I would also completely remove and clean (DriverSweeper) the drivers for the video card and let it run on the generic W7 WDDM1.1 video driver for a while. Then afterward install the newest nVidia drivers fresh.
Make sure you are running the chipset drivers and AHCI drivers from Gigabyte. Make sure all the other drivers are the most current drivers from the vendors website, not from the Windows install or from Windows Update.
Good luck!