memory - Can i install more ram than product specs says it will handle?

I have a Compaq Presario sr2017cl running windows 8 pro 64bit, Athlon 64x2 cpu. Specs. says I can only install 4x1g of ram. I want to know if I can put 4x2g of ram into my machine. If yes do I increase MHz, this is what I have now installed 4 sticks at 1g PC2 5300 (667 MHz) DDR2 DIMMs. Motherboard PASUS A8M2N-LA,
800w PSU.