Originally Posted by W1zzard
... 64-bit os has not much of an advantage, ...
On your test rig it most certainly has.
Just count the RAM available:
Regular "CPU" RAM: 3x2 GB = 6 GB
Graphics RAM (for this test): 2x2 GB = 4 GB
Total: 10 GB
A 32-bit OS can use a maximum total of slightly less than 4 GB, which probably is the reason some of the gaming tests were totally unable to run at all. (All addressed RAM available for either the CPU or GPU, none available for the other?)
To address all that RAM you'll need at least the Business version of 64-bit Win7, which can handle up to 12 GB if I'm not mistaken. (Home Premium can only address 8 GB.)
32-bit OS is just fine as long as the total RAM is 4GB or less.