Some people have found that when they upgrade to Mavericks – Mac OSX 10.9, a free download and install – their computers slow down a lot. This sometimes seems to be the case with older Macs. By older I mean more than a couple of years old. Although Mavericks will run with 2GB of RAM as a minimum in reality a bit more is required with 4GB being the realistic minimum. Even so, older computers still struggle.
The answer is to put more RAM in it! As much as possible. Older machines have a limit so just get as much in there as you can and you should find that the problems are over for an outlay of about $100. Well, the operating system was free….!