Yeah, RAM is okay, but with a 128 in already it should't take a couple of seconds to do anything - let alone get a response from the desktop. I think something else is wrong.
You could run system monitor to see if it is taking a lot of CPU power to get things done. You might try and run some kind of program in DOS to see if you have power outside windows. That will tell if it is hardware bogging it down or windows. Then you'll know a little more.