I have only tried msconfig, and unchecked many start up programs but still get about 2.25gigs of memory used up after using the computer for a while(few days). The only thing that is open is firefox which takes up about 185mb for 3 tabs open and 63 different processes other than firefox open for some reason. I have 311gigs free out of 586gigs and have Windows Vista home premium 64-bit.
Windows Vista will always consume 99% of memory, it does this for prefetch, caching etc. This is good, it helps your computers performance, it frees memory from prefetch etc, as your applications need it.