Rainbow spinning ball comes on all the time

Question

I work in photoshop, on pretty huge files. about 4 GB, the maximum it can take. I have 8 gb of ram (although I know CS2 can only take advantage of 3 something GB). The thing is that my computer is getting slower and slower, and I get that spinning rainbow ball ALL THE TIME. It's driving me crazy. It's come to a point now that when I start up the computer, photoshop won't even open a file. It will just spin that rainbow ball and when I go "force quit" it says "photoshop (not responding)" I restart a couple of times and then finally I get it to work.
What's a good FREE utility to download that can check for file errors? I haven't run any sort of check on my computer ever.
G5 dual 2.5ghz   Mac OS X (10.4)   dual display

Answer 1

The only free utility to check for disk problems is Disk Utility which is included with your Mac. There is a good utility called YASU which can be used to rotate log files and clean caches. I have never used it to clear caches as that is a troubleshooting step and not needed for routine maintenance. You might want to read about basic maintenance here:
http://www.thexlab.com/faqs/maintainingmacosx.html
Here is a link to a FAQ which has very detailed information about the SBBOD and what you can do about it:
http://www.thexlab.com/faqs/sbbod.html