Most hp/compaq machines with onboard graphics don't let you adjust the video memory size. As the motherboards are usually hp/compaq specific models there aren't many bios's (not many, if any) around. Check out the hp site under "drivers and downloads" to see if there are any bios updates for that model. I wouldn't hold my breath though, some of the onboard graphics models don't even let you disable the onboard graphics if you have a video card installed, let alone change the video memory size!!

would other boards with onboard video card let you allocate more memory into video? And if they did im supposing the extra memory is taken away from the ram right?

Unfortunately, Compaq is noted for having "proprietary" components. They design their BIOS and other components such that you almost always have to return the item to them for work. And...most video cards are only upgradable with proprietary memory upgrades or offer no upgrade options at all. If your card is not integrated, you could look at replacing it. Otherwise, you're probably out of luck.