Windows 8.1 Final - installation

Hi, Excuse me if this is the wrong place for the post, but was best suitable for me in the morning. When I upgraded from Windows 8 Final to Windows 8.1 Preview, it removed my UEFI Windows 8 Installation. To my knowledge, it also changes the MBR on the harddrive. After 5-10 minutes of panick attacks and such I fixed the issue in my BIOS, with some config changes. My question is, since MS...