There is no "programs" folder as executables could be in a number of places. If you want a "programs" folder just create one and add it to your path.
You can use the "which" command to find out where the executable is located.
Note that using "Pidgin" or "Kopete" won't work, it's not Windows and uppercase/lowercase matter. "Pidgin" is not the same file name as "pidgin". In fact you can have two completely different files, one named "Pidgin" and one named "pidgin", since that's only the same file name in Microsoft's world.
If you want to find anything, anywhere in the filesystem, then install "mlocate"
After it's installed run
That will go through the filesystem and create the database. Then you can use
and it will find every instance of that file name. You'll need to run updatedb again after installing something new, or add it to crontab so it runs every day to keep the database current.