Please post screenshot for : edit > Preferences > Scratch Disks
How do I do that
Ok, if you don't know how to post a screen shot, for now just tell us how much free space is on your disk. If you don't know how to tell, that's probably the problem; please tell us what system you have.
The Photoshop scratch disk uses the space available on your hard drive. What Photoshop is telling you is that your hard-drive is so full that there is no room left for Photoshop to use. If you have a single hard-drive. you really have 2 basic options.
1) Clean off the C drive. Delete unneeded or duplicate files, uninstall unused programs, ....
2) Install a second hard drive.
To check your disk space on Windows 10. Bring up File Explore by pressing the Windows Key and the letter E at the same time. (Similar to using a shift key). On the left you will sell a list of folder. Click on the one called "The PC".
Look under "Devices and Drives". They should have bars next to the drives showing how full they are. If any of them are red, that is likely your problem. (Red means it is getting full).
I am cleani up my hard drive to see if that make a difference .. I've taken a screen shot of the prefrance box , I just don't know how to post it on here