Bob, what ed is saying is you make a bootable CD-R of the Ubuntu OS, then reboot the PC to the CD, and voila you are running Ubuntu from the CD, not Windows from the HD. It runs slow when it has to seek to CD, but otherwise it's interesting. It would take me some getting used to in order to use it everyday computing. But as a music server where you would never touch it outside your player app, could be OK. It will run much faster when installed on HD.
It's free to try it, moneywise that is. It will take time to download the big iso file to make the CD, and another 5 minute+s to boot.
I think there are some apps on it, and a browser. t would not run roblox.com or webkinz.com so it was not the solution I was seeking when i tried it last. XP SP3 is killing my kids old puters.