A machine running XP with 2Gb RAM will probably not be stretched since that is at least 4 times the recommended basic amount of RAM. If you open task manager and go to the Processes tab you can see which processes are using CPU. From the view menu choose select columns and add any memory columns you want to see the information.
Obviously, looking at the performance tab gives you a summary of how much RAM and page file usage. Not a great user interface but it`s all there!