If you can get decent results from FS2004 then IL2 should run well. I run both under XP.
In your case, I'd start going through your hardware drivers, in particular your graphics and sound card ones to make sure they are up to date.
However, my gut feel is that it might be your settings on your graphics card. IL2 is an old game and has no settings for some of the more advanced features of the graphics card you have and it's defaulting to the most intensive ones.
It might be useful to know more about the machine specs.