@dcommand3r I'm not sure as to why you would clear prefetch data, it's a good thing, really.
Anyways.. after a clean install of the 64-bit version of Windows 7, I booted up and clocked the memory usage at 700~800MB. Now that I've been using Windows 7 for a month or so, the needs have grown, and it boots up with 950MB of memory being used. I've never actually seen Windows 7 go beyond 2GB, considering my Vista install boots up to 1.2GB.
I'm not sure if this affects my memory, but I do have a 1GB ReadyBoost implementation in place, alongside my 8GB of memory.
I haven't disabled any core features of Windows 7, either :P