BSOD 0xc000021a, update meant to fix BSODs causes BSODs

January’s Patch Tuesday delivered BSODs with stop code 0xc000021a after reboot — the irony being that this update was partially meant to fix a BSOD issue from December. Installation failures stacked up with errors 0x800f0831 and 0x800f0988. The update designed to stop your computer from crashing instead made your computer crash, which is the Windows Update equivalent of calling a plumber who floods your house. Microsoft needed until February to ship a proper fix.