Under normal circumstances, assigning a drive letter to a disk partition will not affect the data in the partition, nor will it cause data loss.

If data is lost, there is something wrong with the partition or hard disk. The data is lost, you can try to retrieve the file with data recovery software.

Drive letter modification:

Right-click on my computer, there is a management option, you click it,; There are disk management options, you just need to select the drive letter you want to change, right click, and there are options.