This weekend, I was asked to look at a system that wouldn’t allow the owner to use a USB External Harddrive (Maxtor Personal Storage 3200, 160GB). It was correctly seen by the machine and available in device manager, and the disk management utilities. However, it wasn’t assigned a drive letter by default, and attempts to assign it one failed. Windows would indicate that it had a drive letter but it never showed up in Explorer and reboot or refresh the disk management list and the drive-letter would be removed.

In the Event Viewer, I found the following error:

Event ID:270

Event Type: Warning
Event Source: PlugPlayManager
Event Category: None
Event ID: 270
Date: 7/10/2007
Time: 7:54:53 AM
User: N/A
Computer: computer
Description:
Plug and Play user-interface dialogs have been suppressed in Factory Mode.

After searching the internet, I found a reference to this message, and a “FactoryPreInstallInProgress” registry key that appears to have fixed the problem:
http://forums.techguy.org/…

Details:

Under the Startup key, deleted the
“FactoryPreInstallInProgress”=dword:00000001

Deleted the entire
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Factory key.

Reboot, and it detected the hardware and displayed the balloon help indicating that it was successfully connected to the system. The USB hard drive was given a drive letter and everything worked as expected.

According to Microsoft, we as consumers shouldn’t see a system in this state. However, this particular user had a replacement e-Machine sent to him when his original failed, under warranty. I am guessing that some e-Machine technician didn’t complete some final step (removing this key/etc) before boxing and shipping the system out.