I've taken a series of Screen saves of DevMgr.  The "WD SmartWare Virtual CD Manager for Windows Web Release-v1.0.8.3" that enables/disables the Virtual CD (VCD) is a standalone ".exe" that apparently doesn't install itself (but take notice in #2 below of the WD Drive Mgmt device at the bottom of the DevMgr list).
1) The first screenshot [DevMgr (no WD MPE)] does not have the WD MyPassport Essential (MPE) USB drive plugged in.  
2) The next screenshot [DevMgr (+ WD MPE, VCD enabled)] has the MPE plugged in with the VCD already enabled.  There are devices under "Disk drives", "DVD/CD-ROM drives" and at the very botom, under "WD drive Management devices", the WD SES Device.  Note, in the properties shown, both devices under Disk and DVD/CD drives are associated with the "WD SES Device".
3) The next screenshot [DevMgr (+ WD MPE, VCD disabled, no PwrCycle)] is just after running the VCD Mgr witout power cycling the MPE.  Note all the MPE devices are removed.
4) The last screenshot [DevMgr (+ WD MPE, VCD disabled, PwrCycle)] is after unplugging and plugging the MPE back into the USB.  Missing from the devices is the just the DVD/CD-ROM device.
Going along with your suggestion above I think the next step might be to re-enable the VCD and then UNINSTALL, from DevMgr, each device.  The question to you is what should be the order of uninstalling those MPE associated devices?  That followed by a reboot to see what happens.
Nelson