Car shows. I have more in the yard (the wife's idea), on the stairs leading to the basement and at Chipmagic.biz . .. Jeff kidnapped them!
I started with online gaming and a game machine I built myself. I could not afford the price of the pre-built machine I wanted so I assembled my own.
I generally did 1 -2 refreshes of the game machine, new CPU, more memory, faster hard drive, current generation video etc then they became obsolete so I migrated them to the "backup" in case my main machine failed and for when the kids came over and we did group on line gaming. Over time, they accumulated and I discovered different uses for each so I now have dedicated machines for specific tasks. They stay busy doing their tasks or I use them in parallel with gaming. Like my main video ripping machine is generally ripping music or video while I am playing online.
The servers just kind of grew as a result of our love for movies. We had ~200 VCR tapes that we gave away and replaced with DVD when that technology came along. One day we had 300 DVDs and soon we had 500 . .. and you can never find the one you want to watch. It became a labor intensive task to catalog, manage and maintain the library. Along came iTunes and Apple TV. We went online with all our music and video. That resulted in a lot of painful learning and soon the need for a server that could go from 500 gig to 8 TB without loosing data. The disk management software in Windows Home Server (the first version, not the current version) allows you to grow the disk size as large as you need it to be. I went from 4 internal 500 meg drives (2 TB total) to 4 each internal 2 TB drives and a total of 8 TB of storage space.
But then I needed to provide for backup, so I have paired servers.