Got a 2008 Mac Mini as a gift—What can I do with it?

A kind neighbor gave me a 2008 Mac Mini along with an AirPort Extreme. The Mac Mini is completely wiped, so it doesn't have an operating system installed. I'm thinking of repurposing it for one of the following: * Setting up a local network * Using it as a hard drive * Installing Windows to play old games Would you recommend any of these, or do you have other ideas? I'm 100% ignorant on any of these Also, if I decide to install macOS, where can I find a compatible version for this model? Any advice would be greatly appreciated! EDIT: It's a Mac mini g4 /1.25