What type of Laptop? Make and Model needed.
You CAN upgrade the video card on SOME laptops: like my Acer Aspire 5920G. It has an MMXII video card slot, and no onboard graphics. My other Acer Aspire 5920 (no G) has integrated graphics (chip), and is NOT upgradable (and it failed).
If you can upgrade, you are limited by the BIOS of the laptop motherboard to how high you can go. I am "limited" to a NVidia 9600M, with only 512MB DDR3 memory.