There's an easier way than that
Move all of the stuff out of your Desktop folder (in your user folder) to the OS 9 desktop folder. Then delete the Desktop folder out of your user folder, then go to the terminal and do this one:
ln -s /Volumes/OS9/Desktop\ Folder Desktop
(that assumes that you
1)are in your user folder when you issue the command - you will be if you just opened up the terminal, otherwise type
cd before you do that,
2)OS9 is the name of the OS9 partition - I'm sure it's not, so replace OS9 with the actual name, and
3)it's
not installed on the same partition or drive as OS X. If you installed OS9 on the same partition as OS X, I
believe that Classics desktop folder is simply
/Desktop\ Folder - use that one instead. You should verify that first. I don't have them on the same partition/drive, so I'm not sure
)
What this does is make a symlink (think Unix's alias) from OS 9's Desktop folder to your user Desktop folder. You may or may not have the usual icon for the Desktop folder in your user folder after doing this one.
After doing this one, you'll need to log out then back in before the Finder will notice the switch. After this, you'll always be using the OS 9 desktop folder as your desktop folder. Note that whatever you place there under OS X will be there still if you boot into OS 9.
Note that this little trick can also be expanded to have ONE desktop for every user. Just a little sidenote on doing this: although one user won't be able to delete another user's stuff, they can place them in the trash! So this may be a good thing or a bad thing.