deactivating / removing a user in different format

Hi,

This is regarding deactivating / removing a user which I have created using different format.

In our project we are following a certain practices like (firstname.lastname) in lowercase etc.

Handling one of the user creation request , by mistake I entered a user login id and clicked the save button.Next time when someone pointed out that the id format is incorrect I dont see an option to edit the user-id and it allows me only to change the user name.

Hope this is a known issue and any suggestions would be welcome.

Regards
Anoop