32-bit OS's can not use any more then 4GB of RAM. That includes addressing to hardware. In most circumstances, the PCI and PCI-E busses are responsable for eating about 1GB of that space [varies depending on the exact motherboard layout].
The only way to use all your RAM is to move to a 64-bit OS.
like to ask 2.98gb out of what? i would assume 2x2gb sticks,
thou its possible to have 1gb+2gb sticks.
also the biggest mistake i seen is when people max video ram size on onboard video card (as stated above) if you can set it to 512 or 768mb don't mean you have to,
128mb is plenty, maybe 256mb if you play some games.