Windows 7 32 or 64 bit?
Regardless, unless you do some fairly intensive work on your machine, you won't see much of a benefit above 3GB of RAM. Though, with as cheap as RAM got in two month's time...It certainly couldn't hurt to add some while it's cheap. Just remember to pick up the same or nearly similar model. All of your RAM must run at the same speed, and it will always run all of your RAM at the speed of your slowest stick if they are different.