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#51
It's highly likely it is the motherboard, but there are a couple other small possibilities. You could Clean Install Windows 7 (after backing up your important data or creating a system image, of course) in case it is a Windows problem. The other two possibilities are CPU and PSU, but your symptoms do not suggest these, so they are unlikely.
Given that the crashes point to RAM, it could also be display card RAM. Use the |MG| Video Memory Stress Test 1.7.116 Download to test your graphics card memory. Let the memory test run for at least seven passes; the more the better.
I realize you probably just want to be done with the problem, but I want to make sure we are thorough so you do not end up with the same problem after you get a new motherboard.