How much for a geforce4?

You can't just swap cards in and out of a laptop like you can in a PC, because mobile video card parts aren't sold publicly. They are sold to companies who install them into their own notebooks (I.E. if you have a dell comp, you'd need to ship the laptop to dell to have them install it.) There's a few exceptions, but that's like 1% of laptops, at best.

That 1% exception would be alienware.