I have come up with this remedy for the drive letter disappearance issue after closely studying My Passport Essential which I own and it may work for you guys as well.
Important: This guide is only applicable on external drives that do not suffer from a hardware issue.
_ First the background: _
Scenario 1 (The Slowness)
My Passport devices are somewhat lazy and take awfully long time to startup when power applied from its USB port. Windows drive enumeration process is taking place rapidly and subjected drive simply incapable to identifying itself to Windows within the given time slot. Other branded or unbranded drives which do not possess hardware drive encryption perform faster on drive enumeration process and do not exhibit this issue. On the given time My Passport only capable of indicating USB interface data and the drive type to Window 7 etc. As a result, Windows mark these drives as empty and not bother to issue a drive letter.
(When My Passport is connected to Windows PC for the first time, Window will allow ample time to ID any drive and wait until driver installation completes. The average user will not experience any issue at this time.)
When the drive is not visible on explorer/Computer, open Disk Management utility and look for the drive corresponding to My Passport and right click and choose, make partition active. Then assign an upper order drive letter. (E.g… W for WD) Do not assign lower order drive letter such as E, F, G and H so on) Now open windows explore (You should see your drive here at this time) and click “Organize” and the choose “Folder & Search Options”. On folder options click “View” Tab and unchecked “Hide Empty Drives in Computer Folder”.
Scenario 2 (Drive Letter Conflict)
By design, Windows assign drive letters to drives dynamically. For e.g… System partition will be C: and probably D: will be assign to either your second partition or to your CD/DVD. And then next dynamically assigned drive letter will be E:. When initially My Passport is connected to the PC, Windows will most probably assign letter E to My Passport if E is free. Next you may disconnect My Passport and connect another drive (may be a flash) to same port or another. Window will reassign letter E to that drive if no other drive is attached to your PC. Now again you need to access another drive… let’s say X branded USB drive. And the letter E: will be assigned to that drive as well.
Now you want to connect My Passport back in to your PC while other drive is connected or disconnected. (Remember X branded drive had stolen drive letter E: from My Passport) While Lazy Passport getting ready to ID itself to Windows, allocated time slot passes and eventually Windows will mark Lazy Passport as an “Empty Drive”.
Use the remedy described in the previous Scenario. So there will be no chance on drive letter conflict.
Scenario 3 (Windows XP – Copy and paste from Microsoft Support site)
This problem occurs when no device is connected to a USB port. That makes the USB driver set the Open Host Controller Interface (OHCI) controller to a suspended state. When the OHCI controller is in a suspended state, it cannot always detect when you add a new USB device to your computer.
To fix this problem on a Windows XP-based computer, you must be running Service Pack 1 (SP1) or later. To determine if you have Windows XP SP1 or later, click Start , click Run , type winver , and then click OK. If SP1 or later is not listed in the About Windows dialog box, then use Windows Update ( http://windowsupdate.microsoft.com)) to install the latest service pack before you try to fix this problem.
Steps to fix this problem
Create a new registry value that prevents an OHCI controller from entering a suspended state.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: 322756 ( http://support.microsoft.com/kb/322756/)) How to back up and restore the registry in Windows
To create a new registry entry that will disable the Selective Suspend feature of the USB hub driver, follow these steps:
- Click Start , click Run , type regedit , and then click OK.
- Locate and then click the following key in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\USB
- On the Edit menu, point to New , and then click DWORD.
- Type DisableSelectiveSuspend , and then press ENTER.
- On the Edit menu, click Modify.
- Type 1 , and then click OK.
Note This setting affects all USB host controller drivers in the system.
If the value of the DisableSelectiveSuspend registry entry is set to 1 , the Selective Suspend feature is disabled. Additionally, the Allow the computer to turn off this device to save power check box does not appear on the Power Management tab for the USB Root Hub.