Unfortunately, that depends on the laptop, if it has a spare AGP or PCI slot where you can "add" devices, not really upgrade them. I have a HP Pavillion laptop, which also runs Vista (btw, i like Vista better) and has greats specs: AMD Turion 64X2 Dual 4.20GHz, 1.9GB system RAM, 250GB HDD.. sounds like the ultimate gaming laptop, right? Wrong. My VRAM is only 64MB, GeForce 7150M. The best game it can run at maximum graphical settings is Half Life 2, it can't even run Halo 2 or Crysis, which is really disappointing. I've asked around (Gilmore and some computer shops here in our place) and they're saying one thing: It depends on the laptop you bought, but most laptops cannot be upgraded.
I suggest, if you're into gaming, buy a desktop instead. It'll cost you around 25K-30K to buy an ultimate gaming PC. Or if you have LOTS of money to spend, buy a laptop that has the latest cards. I think that'll be around 35k-50k, depends on the brand, really.
Anyway, i'm content playing CABAL ONLINE and DoTA;D