Fortunately, laptop hard drives are the one really generic part (aside from most memory) that you don't have to worry too much about replacing. I just pricewatch or call dirtcheapdrives and buy the closest capacity match, which is usually somewhat larger. Depending on the model, you may be able to really upgrade to a much bigger drive on a replacement, but you probably won't get the benefit of a faster interface on an older notebook and the BIOS may not recognize most of the capacity, so there's no point in spending much more than you have to. Laptop hard drives can be extremely easy to replace or moderately difficult. The difference lies in how they are accessed. Many older notebooks allow you to replace the hard drive through a single-screw access panel on the bottom of the unit, sometimes it's right under the battery or the RAM. Other laptops require that you crack the body open, remove the keyboard or the motherboard (assembly varies from manufacturer to manufacturer), really take the whole thing apart. The interface for the IDE cable on the drives that come out easy is often fixed in place, so the drive basically plugs in, while the drives that require you to take the whole thing apart often make remove the connector on a flexible (and fragile) flat cable before removing the drive. I have an illustrated guide on how to replace a laptop hard drive of the easier type:-)
