is program installed

Question

Hello,

I have been playing with the registry to to look and see if Excel (or any other program) is installed.  I can directly check the registry path where Excel is installed on my system and return the key, but this would not account for any other version of Office or Excel. I can account for the couple of versions I know of.  I guess I would like to be able to open up the Local Machine registry and loop through all of the Microsoft applications and look for 'Excel', but I haven't been real successful.  Does anyone have any ideas?

By the way this is in C#....

thanks,

Chad