Man oh man. Two steps forward and one step back for you. Really sorry you're having this problem.

When I installed 10 the first thing I did was open Biab and it opened right up, I had to do absolutely nothing but double click the icon. I also have Avast but I did write about how I had to completely uninstall it before Win 10 would install. But after that I put Avast back on and no issues whatsoever. Maybe completely uninstall it and give that a shot. Sometimes A/V software can really mess things up. Look at Furry with Panda.

As far as the directory tree, it's there just like 7. Click on the Explorer icon in your taskbar and you'll see the tree on the left. Click on This PC and all your drives appear in the window to the right then double click on your C drive and the familiar directory tree appears. Or, just hover your mouse over the words This PC and the > symbol appears to the left. Click that and the tree appears vertically there without appearing in the window to the right.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.