There is no direct way to remove users from the user list. The thinking behind this was that once removed, HLMSW in unable to reference the user details of items they have edited which are displayed when you click on the vertical text in the Edit Window.
I will look at adding the option in a forthcoming build but in the meanwhile there are 2 things you can do...
1) Old entries can be re-used by simply changing the details of an existing account and saving the key to the shared key directory. This does not remove the old key from the list of names you see when you start HLMSW (see point 2)
2) If you want to reduce the number of names in the drop-down list that you see when HLMSW starts, then all you need to do is to delete or move the corresponding HLMSWKey file in the shared key directory.
Peter (BTMI)