Not Sure how to Do this

Question

I have made a program that hooks into another, using their own API's. Now their API's don't tell me how to locate their program if its installed any place other then the defualt.

Well, I would prefer to have my little program locate their automaticly and not have to ask the user for the install location.

Is there a way I can do this? I have already looked at their registry values and their is not Install Location one like some program put in.

If it is possible to do, could somone point me to a tutorial, or post a code sample i would apperciate it very much.