I mean that Windows is gone. The error saying that the system is not fully installed says that Windows can not boot cause it is not detected anymore. Ther was a change to some of the critical system files that allows windows to boot and work correctly.
Since you at elast get thru most of the boot jsut dont get to a desktop that tells me that it is something with the install. Last known good config might fix it. Since that will restore your PC to a state where Windows last booted fully and correctly. If ont a repair install will replace the Widnows files. Not your personal files.
If that still dont work you will have to reinstall.