Sounds like a good way to make use of old eMachines, at a large discount too.
Finally, the year of the Linux Desktop! (eMachine edition)
Linux Mint is often recommended to the uninitiated and you can test it without installing it, using a live USB image. Boot up of off the USB drive, test it, turn it off, pop out the drive, tun it back on, you're back to your old OS.
Whatever the linux flavor, the graphical part will most likely be called GNOME or KDE. They're very user-friendly, you just need to explore a bit with your mouse.
Games have improved tremendously thanks to Valve and you can play most of them on linux via compatibility layers.