I already updated my laptop which is Windows only and learned that the 1511 update installs like a complete new install.
Good to know. At the moment I'm using Linux either from USB (Fedora) or in a virtual machine (Sparky). I've been thinking of adding Linux to my laptop's HD, but I've experienced strange problems while booting live distros and gave up (sometime they boot, sometime they don't, the installers can't see Windows etc.). Now, it looks like I'm lucky, cause my Linux installation would be already wiped out anyway. I don't get it. Microsoft has announced that it's is Linux friendly now, but in practice things have gone worse.