Not much you can do with a low-end desktop. Mom's hard drive experienced an unrecoverable error and Dad brought it to me the last time he visited. I left the CPU untouched in this one (its unlikely he'll require L3 cache) but did replace the drive with one at 7200rpm, put in a matched set of max RAM, offboard the video and installed Windows 10.
Should give them a few more years out of this box.
