I think looking at the memory usage is a red herring. In general, on modern OSes, if there is unused RAM sitting around, some program will claim it, but if the program is not actually using it (the ram), and another program needs it, the program will give it over.
Not to defend windows... All those updates, to the os and adobe and java... it;'s like a full time job keeping up. And having automatic updates mysteriously turn on is annoying and unsettling.
If you don't want to putz around with computer stuff, And you don't need some windows only program, And you don't mind spending a little extra, get the mac.
Install Linux on your PC first though. I installed ubuntu on my sister in law's laptop after she got a million viruses and it all Just Worked and she hasn't called me back to fix anything since. Here's one I haven't tried, but is for video/audio editing... http://ubuntustudio.org/
ps i'm on a different linux distro right now using 345MB out of 4gig =p