Just did a clean install of windows XP, only installed a couple of things other than drivers and ARMA2 on this hard drive. Before on vista x64, which was reasonably well maintained, did have a few things installed and ArmA2 was not installed on a clean hard drive like this, but still I don't see how that effected the results I got from ArmAII Mark. Here are the test results from the highest mark I was able to achieve with low-medium settings @1920x1200.
XP32 Sp3: 3345
Tune XP 1.5, might as well mention it since I use it with XP, it's very good.