I finally decided to accept Internet Explorer 7 on my desktop, after testing it on my less used laptop. No way would it install. I looked for help on the Internet, and was referred to the Microsoft site.
I downloaded the SubInACL tool as linked in point D of the document, and ran it several times, after having tried the previous methods in the document. No help here.
In method E it said to check the log of the install procedure in C:\Windows\ie7.log. There I saw another kind of error message set than any that I found on the Internet while looking for help. It said:
IECUSTOM: Unwriteable key HKCR\Interface\{34A715……
which means that someone or some program has set the rights of some Internet Explorer registry keys to read only even for sys admins.
I went to Start > Run > regedit and looked up the offending HKEY_CLASSES_ROOT (HKCR) folder and found the key set, right clicked on it and set the rights to full for system admin, including all subfolders. That did the trick.
I also had to disable the virus and spyware control programs and shut Zone Alarm’s suspicious process watch part down during the installation.
After the installation, Windows wanted to shut down. Before doing that, I restarted the full ZoneAlarm and virus+spyware control program.
After Windows reboot, I ran AdAware, virus sweep and ZoneAlarm spyware scans, and several problems were found and corrected.
Done!