W7x64 is crashing but x32 isn't HELP!

Hello and thanks for taking the time to help me out.

I have used the W7 RTM x64 for soe days now with no problem, but as a personal rule I format my computer twice a year. After formatting it the last time, it started crashing constantly while intalling progrmas or accessing my external USB hard drive. The easiest way to crash it is by trying to do the Windows Experience Index test since it freezes the computer when doing the Direct3D 9 assesment, the very first of the process.

I tried using the retail version of W7 x64 and that installation didn't even finish. It just stops when setup is "expanding windows files 55%". Simply freezes.

Then I installed Vista x64. It also fails to install although it finishes the file expansion just fine. After I have inputed the User and Computer names, it reads "Thank You", I click "Next" and then it either restarts or freezes while testing my computer's performance for the first time, which the install process does automatically, unlike the W7 installation.

Finally, I installed the x86 version of W7 RTM and it works perfectly. I have 6 GB of RAM with an Intel i7 920, so running this OS is simply out of the question.

Any ideas as to what the problem might be and how to fix it? I'm thinking RAM, but I am not sure what to do about it or how to test all 6 GB of memory (it's Patriot DDR3 triple-channel, in case anyone needs that info).

Thank you so much in advance.

notsograymatter said:

I'm not quite sure but it sounds like your installation was corrupted. You can try a repair install using the dvd, but it may be the dvd itself, clean it first.

I've tried installing them several times, burned several different DVDs as well. Remember that the RTM version of W7 x64 installs just fine, but stats crashing when I try the Windows Experience Index, I install a program or I just surf the web.