The inexorable drive toward obsolescence driven by new operating systems from Microsoft and Apple can make a perfectly good computer unusable within just a few years. Linux and other similar open source operating systems allow you to extend the life of your computer with just as much functionality and no cost. You can find a list of lightweight operating systems for your older computer at this link. I tried about a dozen of these on the road to finding what would work best on ten year old computers. I recommend the following. The best thing about all of these is that they are free.
For a "plug and play" easy installation on an older computer, I recommend Lubuntu, a lightweight version in the Ubuntu family of operating systems. For an ultra small (256 mb) os that you can carry on a flash drive, I recommend Slax
