Spare machine as file/print share

"if you want to learn linux - by all means do install it. there will be a brief period of enthusiasm followed by long period of grief - most probably, yet it's worth it.

you can use the computer as:

headless download box
smallish web-server [ if you have public ip with your internet connection ]
media center server [ if you have UPnP compatible media players in the home network ]
platform for testing and development of whatever you're interested in - can be central node for a sensor network monitoring temperature in your place or machine gathering stats from stock markets in the local DB.

be aware that you risk compromising the box and it's content if you put it online - regardless of the OS choice.

btw: your q. is probably better suited for superuser."

"Based on your desire to have a useful box, and play with linux, I would go with an XP / Ubuntu (or maybe better Mint) dual boot. I have a dual boot that only ever uses Ubuntu at home for all 5 members of the family and everyone loves it. I have a mostly XP for work but sometimes Ubuntu dual boot laptop that I use for security outside the house (and because I generally prefer linux). And a Ubuntu only box at work that I use in a windows network as network attached storage for all the computers because the box was old and free. Rather than repeating some things that elaborate on these points I will just say ditto to what I said and the rational listed in these two posts.

Cheap NAS for connecting a USB drive to the network

and (don't let the title of the question scare you)

Ubuntu partition not loading

Be really careful though, I started innocently enough now I find myself promoting linux, using almost exclusively open source software for everything on all my computers, and listening to Ubuntu podcasts."