open up regedit, and then navigate to:
HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows/CurrentVersion/Installer/UserData/Products
Under this folder you will find a list of GUIDs, of which only of them is the one you want. Therefore:
While you have "Products" select, got to edit->find
Then type the name of the software you want to find more info about.
This will open up th corresponding guid that you are interested in.