I've never tested this so it will be interesting to see opinions on it but I believe that the shared graphics memory can come out of the surplus XP doesn't use so if graphics are using 512Kb, you only waste 256. Does anyone know that for certain?
Either way, though, I see no need for a third party RAM Disk utility. Pagefile.sys works better if it sits on a separate partition so it can be defragged regularly if the system is in permanent use but if it;s turned off at night, defragging isn't necessary. You can set a pagefile size in Windows' own utility.