While it's often possible to upgrade to larger memory total, the number of RAM modules that can be fitted (ie number of sockets) might be low, so to go from 2 GB to 4 GB means taking out the 2x 1 GB modules and replacing with 2x 2 GB, so you cannot just buy 2 GB but have to buy 4 GB.
Also, not uncommon to need identical pair - so had to put 2x 1 GB modules into the 2 sockets, rather that have it come with only 1x 2 GB, and therefore cannot always switch to 1GB + 2GB
Laptops can be a bit tricky. Depends on the make and model.
While there are other firms doing memory, Kingston is one of the best and has a 'checking' facility - starts off with the manufacturer, then splits into desktops and laptops and model numbers...
Tells you what max RAM can be (and what you'd need to buy for that model).
Of course, you might find you can sell the (current) RAM modules on Ebay if you find you have to replace them with bigger capacity.
Not so sure, SomeGuy, that it is 'slow' for a laptop.
There are airflow constraints or the CPU / laptop will overheat, and a wish to extend battery life, so running the CPU reduces the need for big heatsinks, and while a bit slower than a desktop with a 2 GHz, it's perfectly usable.
Sure, new desktops with 3 GHz clocking will be faster, but they're generally noisier and have big fans and big heatsink fins (if not a fan nearby on the video card, over and above any other fans, or water cooling).