If you can come up with the exact model name, there are plenty of places (including here) that will tell you how much RAM you can put in. At a guess, you could go to 4GB which would speed things up a little simply because of the way most motherboards address memory, but you may be stuck at 3 GB. This sounds like an older system. In reality, you might get most benefit simply by checking out what unnecessary stuff starts when Windows starts, and stopping that if you can.