I have a windows 7 and an xp machine. With 7 it's pretty easy to see whether you have enough memory or not (open task manager and see if you have significant amounts of "unused" memory) but with xp ...

Don't remember if this works in XP, and don't have a machine to test it on right now, but I think that if you sort the list the way you want it, then hold down the Ctrl key while quiting Task Manager, ...