hmmm. I didn't realize it was 4GB total for 32bit devices (i.e. system + video card).
I am about to go to win7 as well and i currently have 4GB mem and my video card has 512MB.
I noticed it only saw about 3.75GB of system memory but I was unaware that it also ignored the 512MB video memory.
All of my parts support 64bit so I guess that answers my question. Especially since I could upgrade to a much large gpu and overall memory.