"Sorry, the desktop folder on the startup disk could not be created. Try unlocking the disk"
There is another possibility. If you're booting from a CD that simply has an installation of 9.2.2
rather than an INSTALLER……
the computer attempts to run from the startup system which in this case is on a non-writable CD.
Boot your computer from 9.0 and look at the files on the CD. If you see the System Folder and such just like on your HDD, there's no installer on the CD. You can confirm the difference by looking at your 9.0 retail disk where you'll see how it
should look.
You can then either:
Drag-copy the 9.2.2 System and Finder OR download the original 9.2.2 from the Forum and install that.
To drag-copy:Make a new folder on your HDD - label it new system or similar. Drag the System folder and Finder from the CD into it.
Open the folder and the 9.2.2 System folder.
Drag the 9.2.2 System file AND the Finder out onto the Desktop.
Put them both back. (You have just "blessed" the 9.2.2 System Folder - it should change appearance and look like your 9.0 System folder)
Reboot with the option key held down. You should see both Systems as boot choices - select 9.2.2 and continue.
In 9.2.2, you can now delete the 9.0 system and Finder
BUT FIRST make a list of you Extensions and Control Panels that are enabled to check against the new System which may be / will probably be different. It will be MUCH easier to sort out what you need/want on or off with a list of your previous set handy.
I have NO idea of your level of OS9 experience. If all of that makes you uncomfortable,
use the other Forum download WITH the installer.That will assure you get a properly updated System and will remove any 9.0 stuff that can mess it up.
You can then pick the updated items you may want from THIS 9.2.2 and drag them over the older ones.
This is what sometimes happens when stuff is crowdsourced - you lose the consistency you normally get from a software developer.
If it had come from Apple, it would "just work"…