I'm assuming VRAM is virtual RAM/virtual memory. In that case on XP, right click 'My Computer', hit the properties button, go to the advanced tab, go to the Settings menu for 'Performance'. From there switch to advanced tab(unless you wish to make the comp run a bit faster) Click the 'Change' button near the bottom. A little window will pop up titled Virtual Memory, click the circle next to 'System managed size' then click 'Set'. Hit 'Ok'/'Apply' all the way out. That is the easiest way to manage the VRAM.
EDIT: You may need to restart comp.