Display issue
changed the display to Parallel Displays in Settings and now I get a blue screen only. I have only one monitor. I have no access to any app or dock. How to reverse? Thanks
I have a iMac with Snow Leopard.
Try resetting the NVRAM/PRAM, as per > About NVRAM and PRAM
1. Shut down the computer.
2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time. 6. Release the keys.
that should return your display preferences back to normal.