This is on a Windows 10 machine with all the current Microsoft updates.
I've been a Vegas licensed user for years and have a licensed version of Vegas Pro 15.
I tried to upgrade to the newest version 311 from 15.0.261 and it failed because it said it couldn't find "vegas 150.msi" which I presume was the old version installer. It's looking in "C:\Users\rbrown\AppData\Local\Temp\SonyInstall_1\vegas150\" but there is no such directory. I also did a search of all of C:\ for vegas15.msi but there was none.
Now my old version doesn't work and I can't install or uninstall it. When I attempt to install 261 it says to first uninstall it, but I can't for the above reason. There doesn't seem to be a dedicated uninstaller.
What needs to be removed so it can do the uninstall or install. As it is I'm completely dead in the water and can't do anything with Vegas. I'm quite familiar with computers and have good backups.