FWIW I was not happy to find that even after using Nvidia's remove everything procedure, this extension remained AND worse still, there were still several hundreds of registry references to Nvidia stuff. Basically ticking time bombs and performance robbing clutter. Same with files in the Windows folder.
For readers, this was not a problem caused by the Win 8.1 upgrade. That extension was improperly handled by the upgrade from Windows 7 to Windows 8 last year. The extension was for an older version of drivers and has served no purpose since then. But it didn't go nuts before Win 8.1.
Anyone know if it would be suicide to delete all the remaining files in the Windows folder from the install that included the bad extension? I was able to identify them all by file create time stamps. I just don't know what bad things can happen with registry entries that might point to them. But none of those files are supposed to be in a Win 8 or 8.1 system, so damned if I do and damned if I don't?