Mary's son upgraded her Mac to OS X Mavericks and now it's running slower. Leo says Mavericks has bugs, but slowing down the computer isn't one of them. Leo says it could also just be coincidental, and that the hard drive is starting to fail.
Mary probably doesn't have enough RAM to run Mavericks. She should double the RAM to 4GB and that will make a big difference. She should also try a clean install, rather than a basic upgrade. She should just make sure to backup her data, erase the hard drive and then start over. Leo also advises taking the Mac to the Apple Store to talk to a Genius.