If you want to dig down and see what might be holding it open, a tool called "Handle from
Sysinternals can be useful.
It's used from a command prompt (under Vista and Windows 7 it has to be one with Administrator rights). Once the command prompt IS open type
Code:
Handle <drive letter of Kobo>:
and the output will show what processes have the Kobo open.
For instance, I currently have my Kobo attached as drive K and a Windows Explorer open to it.
Code:
C:\Tools>handle K:
Handle v3.46
Copyright (C) 1997-2011 Mark Russinovich
Sysinternals - www.sysinternals.com
explorer.exe pid: 1500 type: Section 1098: \Sessions\1\BaseNamedObjects\Groove:FileWatermark:3Xun+atCrYOF674SeEMAXoUjZUo=
explorer.exe pid: 1500 type: Section 10B0: \Sessions\1\BaseNamedObjects\Groove:FileWatermark:cFIpVcw40e60gkoY+gP4pTRPi08=
C:\Tools>