|As it's working, obviously it will accept 2GB sticks. But the motherboard probably wouldn't support more than 4GB in all. As it happens, it is irrelevant - your 32-bit Operating System would not recognize any additional memory.|
You have the optimal setup already and, as it's working, enjoy it.
Unless you have a special need for it I would forget about 64-bit for the time being. I don't think you would gain appreciable advantage to justify the cost.