I downloaded Ubuntu 13.10 a month or two ago and while I like it I want to switch back to windows 7 because it has a larger gaming library. My question is will I run into any problems if I use the reinstallation disk? I don't have an actual Windows 7 disk. The disk says "the software is alredy installed on your computer, use this DVD only to reinstall the operating system on a Dell PC." Will the disk not work since I have Ubuntu installed and not windows 7?