[Wurschtie]

Just a quick word about Win, and the difference between systems.

WinXP is not able to run DX10, DX11, Win 7 is.
Win 7 has a way better load balancing and memory addressing behavior.
Though it doesn't matter whether you use Win7 x32 or Win7 x64, you will be able to use DX10/11 with both.
x64 however will result in better performance as long as there's no x86 garbage in the command set. x64 menas that the CPU can work 64 bits (8 bytes) in one cycle, instead of 32 bits (4 byte) that a x86 system can handle.

Unfortunately, IL-2 CLOD is an x86 exe, which means that the added processing speed will not be used. However, you get other things like memory management, and everything that runs in the background worked in x64 mode, which should in fact result in slightly better performance.
To really make a difference, we would need a x64 executable, though. However, to provide that, the devs would have to change memory management and many mathematical helper functions, which i assume are quite a lot.

And another thing:
In an x64 system, all address values are double the size (64 bit instead of 32 bit), which leads to a slightly higher memory consumption. So if you are just using 2 Gigs of RAM, don't use x64.