Maxing out my RAM

Hi I have a question I just can seem to find an answer to without asking. Is it possible to max out my RAM to 16gb.. and is it worth it? When I bought this computer (an HP) it said it maxed to 8, but recently I've seen 4gb sticks of ddr2. It has 4 slots and I'm running Windows 7 (64) Home Premium. Just trying to figure out what I can do with this pc... and any suggestions on how to maximize my performance would be greatly appreciated!

System specs:

AMD Phenom 9550 Quad-Core Processor 2.20 GHz
5 GB DDR2 RAM
NVIDIA GeForce 9300 GE

Haven't been able to figure out how to get my motherboard, bios... etc. Everest can't figure it out either

 

If HP says 8GB is the max then that's all the motherboard can handle. You already have 5GB, what application(s) are you using that would require more memory than that? I have 4GB constantly being used at %70 with my Q6600 rig and all is fine. Post up your model #, maybe someone here can help you further.