Gray screen with status bar that doesn't complete means it was attempting to fix a problem on the drive and it can't.
This is a complex problem to solve and if your signature is accurate and your on 10.5, then you need to not only do data recovery (if you have no backups of your files off the machine) but likely wind up having to erase and install everything and upgrade to 10.6 at the same time.
If your not comfortable with computers, I really suggest you seek the services of a local PC/Mac software and data recovery specialist/repair shop.
10.6 disk can be ordered by calling Apple via phone, only way to get it now.
Then your going to need to do this to get your files off (if no backup)
Did you try reinstalling the system yet? If not, do that. If you have an up-to-date backup, you should probably just do what is recommended in the section of that document I linked to titled "Perform an Erase and Install installation of Mac OS X as a last resort." If not, there's no way out of your predicament that will guarantee no data loss, but you can try the steps in the section labeled "Perform an Archive and Install installation of Mac OS X."