Fucking hell.
CMN if you install Ubuntu over your windows partition you will lose everything on it.
If you have a separate partition else where with your music on you won't lose it.
You can't install Ubuntu on the windows drive and keep the files on there. It doesn't work like that.
Keep the 40GB parition with your music on for now.
Options are
1. Install ubuntu over your windows losing all the files on it but having already moved the ones you want to another partition (if it's NTFS you then have to fanny about getting the read write permissions in linux to work) or DVD they are safe.
Se the other partition as your home partition.
2. Install Ubuntu over your fedora partition. set the one with your files in as your /home and leave the windows one there for whatever reason you want to keep it.
3. Back everything up to DVD that you want. run the Ubuntu disk. follow the instructions for installing it, allow it to erase everything and start from scratch. set up a 10gb (NickA says 20 but I've only every used a 10GB and been happy enough up to you though) partition for Ubuntu and the rest for for /home. Then copy all your files back to your /home
4. Do nothing leave it as it is and get back to digging your pond you lazy sod
NOTE: When you set your /home folder and set it as a drive REMEMBER to uncheck or check the little radio button that says DO NOT FORMAT or the files will be lost