System reserved partition in Windows 10 Posted March 21 · Edited March 21 by Octopuss I have just tried this in a VM and sure enough, once that partition existed, the CU installed just fine. If it's not present, it fails during reboot after seemingly successful installation. This started some time a few months ago, basically in the 2nd half of last year I guess. I have the usual GPT setup with 100MB EFI, 128MB MSR, and the actual Win partition. I have been doing this for years and it only started to give me problems with this thing. Oh and btw, installing a CU manually works just fine even without the partition. That's kinda bizarre. Something must have changed somewhere but... meh.