For the interested readers:
It seems to me that there is something wrong with this extension. Therefore I suggested you NOT installing it.
If you need some validation controls related to textfields, Radios and Checkboxes buttons, etc, I strongly suggest the (also free) "Yaromat CHECK FORM MX extension".
I installed it and it works nicely. It is easy to operate and the only difficulty I had was to find WHERE the extension was (after installed, for sure). It will be in (Dreaweaver MX 2004) "TAG" panel, submenu "Behaviors" (look for "Yaromat").
ThatÂ´s it. There are many other extension there. I would have a look if I were you.
YaromatÂ´s Homepage: http://www.yaromat.com/dw/