These days, yeah, some laptops "video cards" can be changed, depending on how new it is. But as Allnatural says, you should not do it. If your laptop supports it, check out the website/call the company on which your laptop is supported on. There, you can find out if your laptop supports it. Though even if it does, I'm not sure it can go from ATI to nVidia (assuming that's what you want). But to be sure, check with the company. If it does, you can send it in to them to get it done. Not sure about price though. Depending on what type of deal you got (warrinty and all), you may or may not have to pay for them to change it.
- Modem