Sure, depending on what it is you mean to upgrade, and how far you'd like to upgrade it. Notebook motherboards (like desktop motherboards) usually have a maximum amount of RAM supported. For notebooks, this is usually lower than your average desktop amount. Processors aren't usually user upgradable because sometimes the processor is soldered onto the board. Hard drives can be upgraded, but you can't add extra hard drives (i.e. if you have a 160GB hard drive, you can't ADD another 250GB or whatever... You can only REPLACE the 160GB with whatever capacity you choose). RAM is usually quite easy to upgrade: most manufacturers make it very easy to access the RAM slots (and some don't: Some models have several RAM slots, one of which is located under the keyboard!).
R15 304-00:
http://www.laptopdirect.co.za/laptop_specifications.php?laptop=19822
R21 829-00:
http://www.laptopdirect.co.za/laptop_specifications.php?laptop=18993
etc...
The point is that you'll end up paying MUCH more for a notebook than for a desktop with equivalent specs. Put differently, for the same price, you'll get a much better performing machine when going for a desktop.
If it's mobility you need, then obviously a notebook is the only option. What you need to decide is whether or not mobility really is NEEDED. If you're talking about mobility in the sense of moving the computer to and from home, then a desktop PC with an LCD screen should be fine. If you mean mobility as in taking it to campus everyday, then obviously a notebook is the only feasible option.