This thread has a lot of mis-information and links from google. So I created an account to help educated those that come hear and read this bad info.
There are two types of chips in laptops: A socketed chip, and a BGA or ball grid array. BGA chips are typically what you find in game consoles, netbooks, apple systems, desktop north and south bridges, on board memory, video cards, etc. They have hundreds of tiny solder balls, directly soldered onto the board like this. http://img.tfd.com/cde/_BGA.GIF
Now, In most laptops BGA's are the default for the video card, but there are many exceptions to this as well as some interesting options.
Also it's important to note that tsupersonic and others are incorrect about upgrades on a laptop. There are several things you can upgrade easily, just like in a desktop, including the processor, sometimes the video card, the keyboard, and the display.
Laptop processors are rarely BGA and a quick jaunt over to the specsheets linked on wikipedia will tell you which are and which aren't. With this in mind, you can upgrade any laptop processor to any other laptop processor assuming the socket and fsb match, JUST like in a pc. I'm currently running a 2ghz T7200 @ 667fsb (the max supported on this laptop's chipset) upgraded from a 533fsb t5200 @ 1.6ghz. They're simply both socket M.
Another example of this is my roomate's probook 4530s. It came stock with a core i5 and we upgraded him to a QUAD core i7 2730QM, simply required popping off the back case, heat sync, and new thermal paste.
Display upgrades are also pretty common. Little do most know, there are only a grand total of maybe 10 major LCD Panel component manufacturers and many of them are interchangeable. Also, the connectors are actually ISO standardized, so there are only a few different connectors and they are indeed interchangeable as long as your video card supports the resolution and refresh rate of the panel.
But this thread was originally about video cards, so lets focus on that.
There is INDEED a swappable and upgradeable video card alive and kicking in several machines.
These are called MXM cards, or Mobile PCI Express Module.
You can see plenty of them on ebay and just buy your upgrade if you have the slot for it http://www.ebay.com/...&_osacat=175673
Now, the 4530s is an interesting beast...
It seems that people around here don't realize that sandy bridge mobile chipsets actually contain the video card ON the die of the processor. It's speculated by many that ivey bridge upgrades to the same slot should be able to support a video upgrade.
As for the on-board, or 'discrete' graphics card, the hp probook series, like many others, have a standard BGA chip for the NVIDIA GPU. There is one way to upgrade though... And not, you don't have the tools to solder a BGA chip, look up the cost of a reflow station. You can swap motherboards with one that has the supported card. Keep everything else, including your processor, and just find a mobo on ebay with the nvidia gpu.
Now, some people mentioned external video card adapters!
There is a thing called eGPU that is so big it's even got it's own sub-forum over at notebookreview.com
The layman's guide is here http://www.notebookr...aphics+notebook
But the real technical thread, with over 1000 pages when you're not signed in, is right here http://forum.noteboo...xperiences.html
and guess what laptop is on the list of successful eGPU mods?