MrPingouin's Igloo

Try to upgrade your current one first. There's a chance of being easier than on a tower computer case.
You may only need one screwdriver. The good one tough. Yeah I know it's not exactly what you see on the pic. Anyway.

The two easiest and main parts to change : RAM and hard-drive.

For the ram, don't forget to check what kind of ram you need and how much memory you can put at max. Oh, windows xp 32 bit does only know how to handle 3 GB of ram, don't put more, it would be useless. Most of the computers are now shipped with 2 gigs, it wasn't the case of mine, just 1 gig more and it already sounds like a revolution.

If you have a Core 2 Duo CPU, don't forget those chips can run in 64bit mode, if you need/want to put 4 GB of ram, you'll of course need an xp or vista 64 one.

Second part. What has always been the slowest part of a computer, the hard drive. You might/must have a 5400 rpm hd installed. If you don't mind about autonomy (and don't have a lot of money), upgrade to a 7200 rpm model. But if you have money, you should consider the SSD models (don't take the cheapest models, well, never). I'm opting to buy a WD Scorpio Black model, it's about 60 euros, a good ssd (with not a lot of space tough, maybe 64 or 128 GB, samsung for example) would cost at least 200 euros more.

A lot of computers also have an express card slot (oldly called PCMCIA), wifi or SSD can be put in this slot.

And finally. If you consider upgrading your current laptop, search on google the "service manual", those documents explain you how to completly disassemble your computer.