I opened iTunes as I usually do but, I got a dialogue box saying, "The iTunes Library file is locked, on a locked disk, or you do not have permission for this file."
Go to the iTunes folder (wherever you keep it) and Get Info on it from the File menu. Under the Ownership section, make sure you can Read & Write and that you're set as the Owner. Click Apply To Enclosed Items and see how it goes. I'm basing this off Tiger, but I don't think the Panther layout was all that different.
I just tried doing that, and I got the same message when I tried to open iTunes. I think I may go to the store. I have serious problems with this computer.
The weirdest thing happened, I updated, my iTunes, I forgot to, and now it opens. But now I need a way to get Calculator.app back, I think the "genius" at the Apple store deleted it. (but I figured out about 5 days after)
You could try extracting it from the OSX discs using Pacifist. Depending on how wrecked your system is, an Archive & Install might be quicker and easier.