Help: An Applescript to find out if an application is loaded

I am new in Applescript and would like to find out if theres a script out there that can check to see if an application is on a OS x and OS9 mac.


This will check if iTunes is installed in the computer:

     tell app "Finder" to application file id "hook"
     --> iTunes exists!!
on error
     --> file doesn't exist
     display dialog "Sorry, iTunes not installed at this computer"
end try

Maybe you need some extra info? You can prompt for it to the Finder…

tell application "Finder" to if "6.0" is in contents of (version of application file id "XPR3") then display dialog "Quark 6 detected!"

Which means that the user has installed Quark 6, OS X app, instead Quark 5, classic app.
Check Finder’s dictionary for more info…