Hi Andrew,

Ideally, the installation of ClickYes.exe would do something useful like set a registry value with it's path that you could check.

If that is not the case it looks like you have 2 options:
1) Prompt the user to locate it for you with a browse dialog.
2) Search the entire local drive for it

The search doesn't really seem feasible - bear in mind that it could be saved in a network location.

I would suggest:
1) Try a default path first (like "C:\Program Files\ExpressClickYes\")
2) If that fails, prompt for a user-specified path
3) Confirm the path and save to the registry (so this process only has to happen once)