Red icons appears in all drives Windows 7

Solution 1:

Update: it's caused by a change in the Windows system by the updates in combination with Dropbox. The Dropbox icon from folders is used on all devices. To fix it whithout deinstalling Dropbox I just removed the overlay icons (which I never bothered about):

Use the RegEdit to go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers

You will see a couple of " DropboxExt0x" entries (01-10 for me). You can export a Backup from the whole "ShellIconOverlayIdentifiers" entry and then delete the Dropbox ones. After a restart the issue is fixed (for now).