According to the manufacture, the max supported memory is 2GB. But that does not always mean it cant support more, it just means that the manufacture has not tested that computer with more that 2GB. In my experience, most of the time the system can support more that what the manufacture says, but I cant be certain that it is the case here.
If you use the computer for daily computing only, I honestly don't see how 4GB will benefit you anyhow. Having more memory doesn't make your computer any faster unless your system needs it. My computer previously had 4GB of RAM. I upgraded it to 16GB a while ago. Guess how much faster it was? Not faster at all. But I needed the extra RAM because I run a lot of virtual systems, and now I have plenty of memory to share between them.
Here is what I recommend, while your using your computer for what ever you do, open the task manager (Ctrl+Alt_Dlt) and go to the performance tab. There you can see just how much memory you are using. Im guessing you will probably be using 1 to 1.5 GB at the most. If thats the case, you will not notice an improvement by upgrading to 4GB.
But, you may be able to make the system run better by not installing more RAM, but FASTER RAM. If you download and install Speccy from filehippo.com you can see what speed your memory is clocked at, and you may be able to buy faster RAM with a tighter latency. Then you may notice an improvement.
But now its time for me to be brutally honest. This computer isn't worth putting any money into. Buy a nice new tower that comes with 4GB of ram and Windows 7 for 350 to 380 bucks at newegg.com.
Hope this helps,
Tyler Adler