I have a G3 (beige) with 8.5.1 installed. I downloaded 8.6 in the single file format and ran disk first aid and Norton Disk doctor before starting installation - there were no problems with either. All extensions were disabled except for the base 8.5.1. The installer crashed about three quarters through - about three minutes remaining, resulting in no operating system and major hard drive problems. After a clean install of 8.5 I tried the 8.6 installation again with the same result. I had not had any problems with my Mac in the year since I purchased it. It seems to me there is a problem with the installer or with the 8.6. Norton found all kinds of major problems which I believe it has fixed but it had never found a drive problem prior to the attempted installation. Does anyone have any suggestions or had a similar problems. Thank you.

Sorry to hear of your problems. I have successfully installed 8.6 on my 6100 w/ a Newertech G3 upgrade card. I don't know if this will help, but I hope so: I upgraded a minimal 8.5 folder on a zip disk to 8.6. I then started up from the zip disk. From there, I ran the 8.6 update on my hard-drive's System Folder, restarted and everything is fine.

Thank you for the reply. I tried your suggestion and started up from the Zip, unfortunately it crashed again during installation on the hard drive. I have now reinstalled 8.5 four times, but I still cannot upgrade. Any other help?
ps I am always amazed how helpful mac users are. If only the rest of life worked as well.