In my previous post I enabled BitLocker on both my partitions (Link). The trick now is to reinstall Windows without decrypting the system. In this example my data is stored on the second partition (Data Partition or D:) and that partition is encrypted and must be preserved.
When booted from media. The installer is asking on which partition it will install Windows. Because BitLocker has encrypted the old system partition, we aren’t able to format the partition. Just delete the partition, recreate it, format and install Windows. (Do not touch the data partition). If you want to preserve the data on the old system partition, you have to recover that partition. (Hmmm new post will come in the future )