I'm currently using the Windows 7 and I want to replace the whole thing with Ubuntu. How do I do that without losing ONLY my music and my movies?
First of all backup all those file to another drive that means save those music files or folder in a drive other then C drive assuming Windows is installed in C Drive then go for installation.
Make a bootable USB or DVD as explained on the Official Download Page for Ubuntu .
Go into Bios and change the first boot priority to either USB or DVD , whichever you are using to install ubuntu from.
Insert you DVD or USB Stick and restart , it will ask you to choose either Try Ubuntu or Install Ubuntu in that click on Install Ubuntu.
then it will ask for installation type in that choose Replace Windows7 with ubuntu as shown below -
then press continue and provide the simple informations like date ,user name, and passwork.
Advice never select Encryption Option if you dont know what it is , not important for at all.
hope i have explained everything you want to know.