A Mac Nightmare


A friend of mine suggested to me to use a maintenance software for my boot-up disks called:
Since this person is a very knowledgeable one, I did what he told me to do and installed it on both my computers. The new one (running macOS Mojave) did not have any problem. The old one (running mac OS Snow Leopard) did.
Onyx could not perform its maintenance tasks and told me to try Disk Utility to verify it.
I did it and saw that there were many errors. I tried repairing the disk with Disk Utility but it failed to fix them. I backed up everything with Time Machine and was ready to erase the disk, but how?
I have the installation disk of macOS Snow Leopard but my internal CD drive has not been working for years. I have a USB external CD drive but I was not sure I could use it to run Disk Utility from it in order to try to fix my internal CD. I tried, I was able to get to the point of the installation where the CD gives me the opportunity to open some utilities, among them Disk Utility and run it but it did not fix the problem. I also tried restoring data from Time Machine but it did not work either. The only choice was to erase the disk and it is what I did from Disk Utility on the installation CD. Now I had to install Snow Leopard from CD. I was able to do it and during the installation I was asked if I wanted to restore data from Time Machine and, of course, that is what I did. When finished I had again a functioning Mac running macOS 10.6 with all the data I had saved the day before but I previously had 10.6.8 on my machine! So, I checked updates that I found and installed. Now I have my MacBook Pro working again with a fixed HD and everything works as expected. Logic Pro 9 and all its plug ins are just fine! It was not a smooth sailing among the steps of this process. I had to try more than once many of them and it took me more than 24 hours to fix the problem but I succeeded!