Replacing one of those is tricky business.
With a desktop PC, it's just a matter of removing a side panel and using a phillips head screwdriver to remove the various disk drives. With a laptop? Everything is much much smaller and with little room to work.
Yahoo Tech did a story on this just a couple of months ago. Most folks do not need to buy an extended warranty on their desktop PCs because they tend to last a long long time, be less prone to abuse and easier to replace items when some hardware does malfunction. With a laptop, it is exactly the opposite; laptops tend to be moved around a lot, left in hot cars in the summer and cold environments in the winter. Dust and constant motion are not friends to a laptop. So, it's always a good idea to buy the extended warranty on a laptop. Always!