Thanks for this:
I trying DO 11.8 x64 in Win 7 x64 and suddenly WIN+E and all other programs open windows explorer instead of directory opus. In preferences I use: Replace explorer for all file system folders (recommended)... but no joy. I also completely uninstall DO 11.8 with revo uninstaller and install 11.8 beta 2 and load all default options but still same problem.
After few hours trying to resolve problem I found this thread and notice that I have:
I do not think the "UPB:" entries were put there by Opus. Do you have any tools with the initials UPB? Maybe ones for enabling/disabling components, as that appears to be what it intended to do.
Since those entries are in an invalid format, they probably make Windows give up and ignore the other registry entries in the same place. The other registry entries (without the "UPB:" on the front) are part of Opus, and are needed to divert Win+E to Opus). So whatever renamed them to UPB: in the past is what broke things, but that was not Opus.
Doing a search for UPB ShellExecuteHooks gives me a lot of results relating to malware. Perhaps the computer was or still is infected with something that inserted "UPB:".
Searching for any registry settings or dll names brings up lots of malware logs these days, often of people reporting unrelated things (since they're reporting every detail about their systems for someone else to see if anything stands out).
It could be malware related but don't panic unless something says it definitely is. I did a similar search a few days ago, trying to work out what UPB was, and couldn't find a definitive answer.