Google MEI Folders
I noticed that Privazer was taking longer than usual to complete a standard clean-up (normally 10 minutes) so I had a look at what was taking so much time.
It turned out to be the contents of C:\Users\myname\AppData\Local\Temp\_MEI83642 - thousands of files.
Investigation revealed that if you exit Google Drive by right-clicking the Google Drive icon in your Windows notification area, and selecting Exit, then Google Drive shuts down properly and correctly deletes the _MEIxxx folder.
Unfortunately, it leaves the folder behind if you leave Google Drive running when you log out of or shut down.
I have yet to verify this but it sounds plausible.