I just reinstalled ProntoEdit4 on my computer (been meaning to do that for quite a while since its registry setting got corrupted).

To change the system:

1) Get into Button Properties.

2a) If there is an IR signal listed in the large white area (such as [C] RC5 16 17) then double click on that.

2b) If there isn't then click "Set Ir"

3) Either of those gets you to the Add IR dialog. If the Pronto Hex isn't visible at the botom, click View IR>>

4a) You can edit the Pronto Hex directly, or

4b) Click Advanced to get to the RC5/6 dialog.