Aero is a fancy GUI for Windows that is optional for Vista. Switching it off seems to have cured several persistent bugs for me, as well as freeing up a chunk of memory.
The Creative Audigy soundcard had a stutter that became continuous when running DirectX in a window. It's gone.
Firefox had a nasty though infrequent memory leak that became a disk rattling virtual memory fight after a few seconds. It seems to be gone.
The Internet connection has almost stopped dropping out.