Here is the Easiest Step-by-Step Troubleshooting for You! :)
You have Only to Take the Time of Reading and Carefully Executing Instructions...
- You Need a Second Disk to Set as the New Scratch...
(For example an External Drive or a Drive Partition)
- Hold down these Keystrokes while Starting:
- On Mac Hold down Cmd+Alt and Wait Until "Scratch Disk Preferences" Popup
- On Windows Hold down Ctrl+Alt and Wait Until "Scratch Disk Preferences" Popup
- Set a New Scratch Disk
Now you are free to Change the Disk and Successfully Launch Photoshop!
How-to Save Image as ICO on Photoshop CS for Mac and Windows:
How-to Save As ICO on Photoshop