I wanted to upgrade my windows 2012 into R2. using setup.exe to upgrade, when it was doing compatibility report, it complained about the C:\ not having enough space, the disk itself is 100GB and the setup wanted approx 108665MB more space before I can install R2 into the current operating system. WTF? The disk doesn't even have that much space, and it's already 50GB free, I don't know how to give it anymore space even if I wiped whole thing, there still wouldn't be enough space. Yes I have tired the /tempdrive switch, does nothing. puu.sh/5Y2Rp/7c1edc1fe8.png
Not more, it wants a total of 108.665GB space on the drive, as your current installation will be saved into the Windows.old directory. That backup plus the new installation plus some temporary space for installation summarizes to the huge amount of space required. Windows Server 2012 R2 is not a simple upgrade or Service Pack, but a completely new OS.