Yes Now Go ahead and change drive letter. give it a letter name. That is very common with WinServer on external drives. Give it a name like F or G because C & D are usually used by internal drives, and if you have two cd/dvd drives it will take E & F so my suggestion is give it a G. And if you have partitioned your hard drive into different partitions give them a name as well like H, I, etc.
I had the same problem with my external drive on server 2003. I have 3 partitions on the external drive, so i had to assign name for all the partitions.
Good Luck.
And, It won't damage your data, you will see a pop up message when you do the change but you can ignore it.