Go to Options, Advanced Options, then place your cursor on the theme and press the Menu key, select Delete Application. This works for 3rd party themes only.
Posted from my CrackBerry at wapforums.crackberry.com
I don't see any themes in applications. So the only way to remove tmobile theme would be to use crack mem?
Posted from my CrackBerry at wapforums.crackberry.com
If you mean the T-Mobile splash screen that's shows when you start your BB, that is hard coded into the device and can't be removed. Otherwise, in addition to CrackMem, there are some instructions for removing the OEM themes here as well:http://forums.crackberry.com/f3/how-...-memory-34633/
As mentioned, removing the OEM themes can seriously affect your BB, including bricking it. You can delete the stock themes you aren't using, or that aren't used by a 3rd party theme.