Running Cad in Windows 7

Hello, I am having trouble finding the best settings for Windows 7...and Ive called parallels to try to figure this out but the person I spoke with couldnt speak or understand english so that didnt accomplish anything. My computer is a 15" MBP with the I7 processor, 8gig ram, 500gb 7200rpm hd and the nvidia gforce 330m graphics card. Before I called today and screwed with every setting, windows rated at 4.9 with that being the 3D/business graphics and processor was above 6 with 1 core, 3gig ram and everything set to give the virtual machine the advantage, after messing with everything the processor dropped to 4.8 along with the graphics. I reversed everything and tried more ram and the only thing that gets it back above 6 is letting it run off 2 cores.
The problem I have is I know parallels is using mac resources to run, but does it use any of those to run windows programs? and no matter how much ram I assign to Windows, it will only use 2.75gb with Automatic or Manual set in the preferences dialog box

 

Anyone have the best setup for the memory/hd and other settings to make it run its best while also keeping mac running its best, and is there a way I can change how much memory parallels is taking from the hd while its already installed?