|Changing the cables isn't going to help one little bit.|
The only thing you can do is attempt a repair install, That depends on the installation programme recognising the existing installation on drive D: and not thinking it is on drive C:
If that fails then it is a complete reinstall in the only answer. You may need some recovery software to get any files you need of the disk before you reinstall.
Next time f you need to change drive letters, use the Disk Management function. In the case it would have flatly refused to let you do it because of the problems it can cause.