Maybe this help, someone...
Im having this problems, with some hours of use, my memory its wasted, needing reboots all time... After days of intesive observation I discovered the problem! For me, its the ASUS MULTIFRAME APLICATION that making this happen to Vista, after uninstall this app, vista became now usable!!!!!
Trying to solve I disabled Superfetch, ReadyBoost, and Indexing... No results... After putting down ASUS MULTIFRAME, I enabled again this features, and its working ok till now....
I hope this help someone...
Regards,