Have you forgot the Bitlocker restore key when you want to disable this function in Windows? Superuser Amenti met this once:
I have a HD protected by Bitlocker. Login, password and restorekey are unknown and all I want to do is wipe the whole drive. When I try to boot from a windows installation cd I have no access to the drive since it asks for the restore key I don’t have. Superuser
Another user of this forum provided a solution - Use a Linux live CD from GParted and delete all partitions.
Other solutions like using diskpart command line, or format the drive, or use WinPE system to delete the partition are shared, you could try, and some users found that the command line method with the command
clean didn’t work on Windows 10, if you’re using this operating system, you could try using Data Wiper, the third party data cleaning software instead, or if all the listed solutions can’t access or format the locked volume, try Data Wiper
Download Data Wiper, the installation or the portable package, install it or directly run the portable file from the 32-bit or 64-bit separated folder, and do the following to erase the locked drive:
The you can use Partition Expert or the default Disk Management to Create a new partition on the unallocated space wiped by Data Wiper.