i heard before..this lappy graphics can reach 768mb if using 4gb same type of ram..reason because when u are using same type of ram..ur transfer bandwidth will become double..it's happen when u try on cpu-z.

u can see ur graphics reach 512mb when u changed it at the bios..try set to 256mb..later when u check agian..u will see it will displayed 512mb..its due to the turbo cache on the graphics..

anyway..i still can't confirm about it reaching 768mb yet..but i heard some forum said like that..

other games that can play smooth on this lappy with lowest setting using n610 graphics :
titan quest IT
world of conflict
hellgate london

perhaps 1gb is enuf to run in vista..but i would suggest to hav more than 1gb ram for smooth performance due to the shared memory with your Graphic Adapter..unless try setting the bios to 64mb for graphics card size to have extra ram spaces.