1
Photoshop uses a space on your drive named Scratch Disk to store temporary files, ensure you have plenty of space (20GB+) on your C drive or some other drive you may have attached to your PC.
2
Press and hold the Shift + Ctrl + Alt keys on your keyboard when you start Photoshop to start Photoshop in Safe Mode.
Release the keys when the Scratch Disks preferences window appears.
In there, you can clear out the scratch disk or move the scratch disk to another drive.