Double-clicking the reg file here will fix things without the need for system images etc:
The question is the cause, which we suspect to be antivirus killing the installer when it isn't a version they recognise, or possibly registry "cleaners" corrupting the InstallShield data. It seems to be different causes for different people.
Sure, one wants to find the cause eventually, but my comment is more general. The cause of a non-working system doesn't necessarily have to be Opus. We are off topic now, right?
Somebody in the other thread mentions reinstalling windows as painful, but eventually the quickest solution.
If I had a need for a quick solution, it would be restoring an image. Certainly everybody is not going to have image backups, but I find it almost unbelievable that technically competent people with the need to have a system working again by the beginning of the work week don't have them.
In most cases, it comes down to either ignorance or (more commonly) time and economics.
For example, I know you're referring to my post about having a "non functional system" on my main work PC after trying to install 12.14, but my current boot drive is a 1TB SSD, which is packed with things. For a boot drive backup, you kinda need full backups each time as a restorable image, which rules out incremental backups. Having the time to backup that much on a daily or weekly basis is problematic at best, and drive storage is always going to be an issue.
As it happens, I fixed my issue without a re-install, but if you want to throw backup hard drives at me for free, I'll happily follow your suggestion in future.
Another factor is you might not notice a problem until long after whatever it is has gone wrong, at which point it might mean trying several backups to find a working one, and/or going to such an old backup that reinstalling might be less work.
Regular backups are great but don't always solve things.
(Plus things like MS breaking system restore for months in Windows 10, and never fixing it so the backups made during that time could ever be restored, AFAIK. That was fun when I depended on it.)
I've never used a backup or restore solution that's part of Windows. Always third party imaging software.
On the point about having a 1 TB SSD, I have a 1 TB HDD, but I don't backup the whole thing. When the issue is recovering from something breaking Windows and the breakage is discovered relatively quickly, I'd restore just the Windows partition. It may be a little easier for me than for many people to say that because I keep all my data/personal files on partitions other than the Windows partition
You really should be able to restore from an incremental backup (you need to have previous backup(s) of course). For handling windows/boot partitions I suggest R-Drive Image, it served me well and has useful cmd-line api as well. For data partitions I recommend doing robocopy.exe mirroring with the windows "Previous Versions" feature turned on (for the history).
Keeping the windows partition as small as can be is what I suggest as well (this includes around 33% free space). It really helps handling emergency situations. If partition got too small, firstly try to de-clutter (use WinDirStat for help), then consider a partition resize in disk manager.
I actually try to put everything onto other partitions which is not required for booting, win-updates and random apps will work against you. Still, all boot partitions (around 80-120GB) here backup within 20 minutes via LAN. These are 6-8 years old windows installations with every software installed you can think of - so I'm quite pleased with the outcome of "keeping it small".
True. I use Image for Windows and related programs from Terabyte Unlimited. To keep the incremental chain from getting completely out of hand, I create full backups weekly and incrementals based on the full daily. I've never had a problem restoring the Windows partition using an incremental backup (which as implied also uses the full backup upon which the incremental is based).
I was probably too harsh in my original "unbelievable" comment.
There is a cost in setting something up, both a monetary cost for imaging software and maybe for hardware on which to store images as well as a cost in time and effort to figure out how all this works.
While I still think anyone who is able and willing to set up a system of image backups will be well served by doing so and will be at much less risk of "my Windows system has become unusable", I understand that not everyone will be able or willing to absorb the financial cost and spend the time and effort required.