An obvious use for an old PC is to wipe it clean and install a lightweight, browsing-oriented OS. With a modest PC, you can run the web-app-inclined gOS, which is essentially a modern, stripped down Linux distribution with a modern web browser and lots of links to cutting edge online services. For older hardware, there’s always Damn Small Linux, which will boot straight from a CD in about a minute on just about any box you can find. Monowall a FreeBSD-based operating system flips any PC with two network cards into a superrouter.”]
Source: https://gizmodo.com/dealzmodo-hack-get-some-use-out-of-your-useless-old-pc-5085572