I came across this while researching the problem, but wasn't sure if it would work and didn't want to try it if there was really still a problem with the machine.
3- Launch RegEdit from the Start menu's Run dialog and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrenTVersion\Explorer. If a subkey named driveicons is present, open it; You will find a subkey named C ,, Delete this subkey , this will return the C drive default Icon so the red icon will be gone.
Could this be a way to get the icon back??