Mess around with Windows partitions enough and you’ll get in a situation where Windows is otherwise undamaged but refuses to boot. Here’s a common fix. (As always, back up your data before touching drive partitions–a single mistake can easily erase everything.)

Step 1. Create a recovery USB drive if you haven’t already.

Step 2. Boot off the recovery drive and go to Advanced Startup Options > Command Prompt.

Step 3. Type:

bootrec /FixMbr
bootrec /FixBoot
bootrec /RebuildBcd

Step 4. Restart and attempt to boot again. If this didn’t work, see here for more helpful terminal repair commands you can try with the recovery drive.