Holy cow, I wrote a book!
Windows XP ships with a number of icon overlays.
The black clock is particularly baffling because you sometimes see it even if your
system is not equipped with Hierarchical
Storage Management. When this happens, it's because some program (typically a
setup program) didn't check error codes properly.
CopyFileAttributes(LPCTSTR pszSrc, LPTSTR pszDst)
The above code fragment fails to check for an error code from GetFileAttributes.
It so happens that GetFileAttributes fails by returning the value 0xFFFFFFFF.
If you fail to check this error code, you end up setting every possible attribute
on the destination, including FILE_ATTRIBUTE_OFFLINE. FILE_ATTRIBUTE_OFFLINE is
the flag that tells Explorer that the file has been archived to tape.