|"im pretty sure it dont matter what kind of ram"|
Actually, it does matter. Density issues are more prevalent in older systems running SDR-SDRAM, especially PC133. However, your system uses DDR-SDRAM...DDR333 aka PC2700.
Clean the contact edge of your RAM sticks, then pop them in & out of the RAM slots to break up any minor corrosion there may be on the slot contacts.
The registry has nothing to do with how much RAM is detected, but if you're using onboard video, the shared RAM setting will have an effect.