Had to reformat my hard drive and did a fresh install of BIAB, then the latest update. Now the BIAB file association is not working. I tried using the file utility in BIAB - didn't work. Tried using the Windows 10 default apps in the control panel and it only shows MG1 and MG2 but not MGU. Using Windows 10 with latest updates and Build 520 of BIAB.

Bob, I sympathize. I think this is a Windows 10 thing. After the latest upgrade I cannot change several default applications. Believe me it's not through lack of trying. I've tried every method available.
Can you change it from here, or is this where it doesn't show:

Another way that might work:

Thanks. When I go to "choose default apps", only MG1 and MG2 are listed. Tried the other way as well, telling Windows what app to open the file with but still no luck. Weird, because I have a laptop with the same version of Windows 10, but an earlier version of BIAB and file associations work fine.

the latest 1803 updates seem again giving us quite a few reasons to revert to windows 7 LoL