Setting up a dual boot would be the best thing to do in my opinion. You can create an extra partition and install Ubuntu on the new partition without touching your old OS. When you want to remove Ubuntu, you can simply format that partition again. The only thing you'll need is a recovery disk of your old OS to reset the bootloader since Ubuntu will install Grub.
Make sure to backup your data before making new partitions.
More information is in the Ubuntu Documentation Windows Dual Boot wiki.
More information on resetting the bootloader when you remove ubuntu: How to remove Ubuntu and put Windows back on?