Your videochipset might just not have the horsepower
Either that or the drivers are crap.
Try and hunt out some more recent video drivers... this can be tricky though, as the manufacturers don't release drivers for laptop chipsets. I have a Dell latitude D820 with an nvidia 7400 go chipset, and I get my video drivers from laptopvideo2go.com - they hack the INI files of nvidia drivers so they will install on any (nvidia video) laptop, not just one make/model.
Sorry no idea where you could find the same thing for ATI chipsets.