(Though not Photoshop related, here's something that might help this situation)
Do you clean out your temporary files often? Ever?
If not, then you'd be surprised at how much space you can gain back by doing so. There's a simple freeware app. that can take care of this in just a few clicks. It's called CCleaner -
CCleaner.com - you can see what it does and download it at that link.
The first time I used it, last year, it cleared out almost 3GB of useless junk.
I've been using it ever since.