First, make sure you can see hidden and system files
Right click on E: and mark partition as active in disk management.
Copy and paste the bootmgr file from C: to E:
Copy and paste the boot folder from C: to E: and tell it to skip over copying bcd and bcd.log when it asks.
Open an elevated command prompt. Copy and paste the following, then hit enter:
bcdedit /export E:\boot\bcd
Reboot. Then open disk management and format C: