>So, even if they just delete the directory and don't do an uninstall. HKEY_CLASSES_ROOT\Excel.Application will report correctly and I don't know what I'm Talking about. Is that about it. :)
>

NOOOOO! Stupid end-user tricks still work just like always - we still find that the end-users play with FDISK, DELTREE, and almost any other unsupervised, loaded handguns that they might not have tried on this particular machine, but ShellExecute() and the Shell.Application Open method are easy to trap, and looking for a directory does not get around the semi-literate programmer trick of installing somewhere you wouldn't expect to find it like on the D: drive or up on a network. Or frobbing directory attributes.