You can't upgrade or change anything in laptops, all components in a laptop are soldered on to the motherboard, laptops use different hardware than desktops; usually marketed as the 'Mobility' version and are usually much weaker than the desktop version.
That is with the exception of RAM which can usually be upgraded, again with the 'Mobility' or laptop version of the RAM which is smaller and have less pins, 200 for DDR2 and 204 for 3.
Hard drives and optical drives can also sometimes be upgraded usually through a service center.
This is the reason people buy desktops, laptops not only can't be upgraded, but their hardware is very horrible compared to the desktop version, for example, the desktop HD 5450 is faster than the laptop HD 5470.
Although, Intel just released the worlds fastest mobile processor, a record, for the first time a mobile processor gets close to a desktop processor in terms of performance.