Re numbering files with letters

[subongo]

Is there a way to rename a large number of files as letters, like file A, file B, file C, and so on? Whenever I use the numbering utility in Bulk Rename, it adds the numbers in brackets. I find the brackets make the file names look too long, so I end up using the utility again to remove all the brackets and extra spaces.

[TheGhost78]

Numbering (10):

Type: A-Z