If Disk First Aid finds and says it has repaired a volume structure problem, and if you can then boot with your hard drive, your problem is solved. If you still cannot boot from the hard drive, you probably have corrupt system software. There is a good chance that this will resolve the problem. Back to the fragmentation problem introduced by OS 9.0.x. There are two kinds of hard disk fragmentation.
Files can become fragmented, and the free space on the disk can also become fragmented.
They are the smallest amount of hard disk space in which a file can be stored. A 6 GB disk, for instance, is usually formatted into 4 KB allocation blocks. A very small word processing document might occupy only one 4K block. If it contains 4,001 bytes, it will occupy two allocation blocks, and so on. Let's say you create a document that occupies three allocation blocks, then another that occupies four, and another that occupies two.