What operating system are you using?
Is your hard drive running low on free space?
How much free space is left on your hard drive?
Is your scratch disk for photoshop set to the Startup drive or some other drive?
I'm using Windows 7, it says that my hard drive is running low on space, I've tried deleting things but the error message still appears and how do I know if it's set to Startup drive?
If you don't have any other hard drives besides C Drive, then that's the startup drive.
You can find out how much free space you have by going to Start>Computer and then under Local Disk (C) it
XXX GB Free of XXX GB
You should have a minimium of 15% free space. If you have a 700 gig drive you should have 100 gig free.
It says that I've got 4.82 GB free of 74.4 GB.
Hard drives are CHEAP. If you have an extra bay in your computer, get a 3 TB drive for very little money, then set your scratch disk to the new drive.