Windows Vista Ultimate is currently installed on the computer. It's a genuine full license version that came in a retail box. I installed it from the DVD disc. Now, can I use the same DVD disc to install Windows Vista Ultimate once again on the same computer, but this time in upgrade mode? Is this a license violation? Is it even technically possible? Will the Windows Vista setup guide just tell me "Windows Vista is already installed you moron" and tell me to buzz off? I mean I'm pretty sure that it won't protest if you are upgrading from Windows Vista to Windows 7 or to Windows 8. But what if you're going from Windows Vista Ultimate to Windows Vista Ultimate (even the editions are the same)? Will it swallow that?... I have never tried this before, so I wouldn't know. When I need to re-install Windows I usually do a disk format and then a clean install on top of that. The reason I ask this is because I have a registry corruption of some sort, and despite my...