You cannot get around the simple hardware limitations of laptops...laptops, especially simple ones (not gaming ones), basicly fail at anything aside from flash games really.
Windows vista 64 costs about $150+ (i think), and you might as well get XP for a slightly cheeper price assuming you even have the HDD room for it. XP will take less RAM so you *may* get slightly better performance, as in, you probably wont even notice the difference if there is any, except maybe in load times.
I would say overclocking is the only possible way aside from turning the graphics settings all the way down, something you probably already did. Make sure your resolution is lowest, all graphics settings are on lowest or off, and anti - aliasing is off. Overclocking however, does not go well on laptops, so I advise against that.
BTW your procesor actually failed the system requirements.