I'm building a universal product trial reset tool for software that is no longer being made since the vendor is no longer in business and I'm hitting a snag:

The idea is as follows:
1. do the software's license control registry keys exist if so, where? store the registry path to the vendor key in a variable since all supported software keys are always under the one vendor key.
1.1 if the software's keys exist, set a variable to 1, if not set to 0
2. if they do exist, which one(s)? store the names of the keys for each product in the variables
3. if none of the three possible keys exist, pop up a dialog telling the user no supported software was found and exit
4. if the one or more of the supported software's license control keys are found, show a the radio buttons dialog with options for each of the three products or reset all. Depending on which products exist gray out the options on the dialog for the products that don't exist on the user's system.
5. based on the user's selection in the radio button dialog, delete the appropriate registry key(s)

I've got the radio button selection figured out so if a user chooses radio option #1 it deletes the vendor key thus resetting all supported installed products, if user choose any of the remaining options it deletes the key for the specific program but not the whole vendor key and its subkeys. where the snag I'm running into is items 1 through 3. Any idea how to accomplish this?