There is another thread on this with another solution in addition to the one I'm posting below, but it may apply to Vista Only. This is a software solution involving 'msconfig.'
Click on Start
Type msconfig in search box and press Enter
If system prompts you to Continue or Cancel, click on Continue
In system Configuration Window, select Boot Tab
Click on Advanced Option Window.
Click check mark on Maximum Memory
Under Maximum memory Type memory to 2000
Click on OK, again click OK to close the window.
click on Restart to restart the system and test the game