too much RAM usage slowing down PT

I've read the optimization and troubleshooting on Windows 7 for m-powered, and most of them I did. There's one other thing that's starting to be an issue for me.. my 3.0 GB RAM installed is being used up by something on my computer often. When my memory goes up to 70%+ usage, Pro Tools is slow.



So this isn't directly a Pro Tools question, but how do you effectively take care of this on a PC?