Photoshop :: Disappearing Hard Drive Space

When I rebooted and reopen the program, it would not allow me to open my project giving me a scratch disk full error. I checked my hard drive and noticed I was down to around 6GB of free space which seemed odd given that I have a 55GB harddrive. So I deleted a bunch of huge multimedia files, freeing up an additional 6 or so GB. Again it ran fine for awhile, then froze. I checked again, down to 3GB. At this point photoshop was closed, so it should not be using any resources. I repeated the process - deleted 7GB of files, reopened photoshop and worked until it froze. When I rebooted, I was down to 2GB of free space. I have freed up a little more room now (6.71GB total) and I can open and work in photoshop. When I do, the harddrive space goes down to around 1-2GB, but when I close the program, it goes back up to 6.71 so clearly this is temporary usage. However, I'm afraid to actually use it because it might freeze again. That seems to be the problem - when it freezes, the scratch disk space that is occupied does not get freed up the way it would if I closed the program of my own accord.

It now has approximately 15-20GB of space that is eaten up with nothing and I want it back.