The simple answer is: you can't. Very, very few laptops have the ability to have their graphics cards upgraded. Unlike desktops, they just weren't designed with that purpose in mind.
Not to mention, even the laptops that can have upgrades, finding the laptop ready GPU isn't super simple, and they tend to be fairly expensive. Probably better/cheaper to buy a new/better laptop.
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Reply to jerreece
Lenovo laptops, like every other brand you have ever heard of, is made by an ODM. Mass market machines are made to fit a certain price point and upgradability goes out when trying to met specific price points.
Limit your future laptop choices to custom builders and you will have that option within limits. Specialty shops like WidowPC.com / FalconNorthwest / Alienware / Voodoo PCwill custom build these things though a top end rig might cost you $4500. For about 2/3 of that price, you can cut out the middle man and go to an ODM supplier such as www.pro-star.com who is a US supplier for Clevo who is the most "cutting edge" of all the ODM's. If you are wondering why all the laptops at all of those specialty shops look the same, it's cause they don't actually build anything ... all they really add is the case paint and a logo. All their models are Clevo machines.
------------------------------If a man speaks in the forest and no woman hears him, is he still wrong ?
Reply to JackNaylorPE