First, open Adobe Photoshop to check to see what hard drive is set up as your Photoshop scratch disk. To do this, go to Photoshop > Preferences > Performance. Then look under Scratch Disks to see which one you are using and how much free space it has.
Following are some of the options you can use to resolve this issue:
If you are getting a "scratch disk full" error when attempting to crop an image, it's likely that you have size and resolution values entered in the options bar for the crop tool, or you entered values in the wrong units. The solution is to press Clear in the options bar after selecting the crop tool but before dragging a crop selection.
In the Preferences tab in photoshop you can select the Scratch Disks category to open the Scratch Disk preference pane. Here you will see a list of all of the drives which are currently connected to your computer. Select one of the drives instead of the current Scratch Disk.Also,you can press Command-Option (Mac) or Ctrl-Alt (PC) when launching Photoshop to change the Scratch Disk.