One note of caution: if you are running a 32-bit architecture or OS, upgrading the memory may not help, because it will be limited in how much it can address at once. (I forget if the limit is 2GB or 4GB; it may be OS-dependent.) At this point I would recommend using 64-bit for everything if possible, and especially not purchasing any systems that are 32-bit only. (Are these even sold any more?)