see if you can change some options in your BIOS to change the dedicated memory size.
update your drivers
. if you are running Windows 7/Vista, disable Windows Aero to improve system performance. If you are running Windows XP, disable all Windows effects. Now you should have a desktop like Windows 2000's one. this should improve a little bit your graphics performance.
If you want, you can try to overclock your GMA with the GMA overclock tool (search on google). it should give you another little boost.
WARNING: overclock your components at your own risk.
Intel's integrated graphics aren't designed to play 3D games, you need a dedicated graphics card to play those games...