How to change CB Filed type

I'm using CB 1.7.1 for joomla 1.5. I need to change one field from multichekbox type to a simple dropdown menu.
This is not possible in the field configuration because the option appears off in grey, and I think that I will had to create a new field, but the problem is that when I create one, in the registration tab, show me the option "Show in the users registration?" say "NO" (in off) and I want to say "yes".
Maybe there are another way for to change type of field, please i need to know how to do it.
I need HELP!!

I have ran into this situation where I needed to change the field type from drop-down to checkboxes. It's easy if you feel comfortable using phpMyAdmin in your hosting control panel.

Go into your Joomla database and find the field you wish to change. It is located in the table:

(yourjoomlaprefix)_comprofiler_fields

Next, look for the column titled, "Type" and change the fields type from multicheckbox to multiselect (for multiple select) or just select (for single select)dropdown box.
Save the changes in your databse and your field should now be a multiselect or select type dropdown box.

This will save you from having to make a new field and populate the selection options as well if you already had data from your users in this field, you will not lose this data when you change the type of field.

If this works for you, how about giving me some positive Karma...