Hi revelationman,
When exactly do you get this error message?
Yes, as you suspect your USB disk drive could be causing the problem.
To narrow down the issue, I would suggest you to try the following steps:
**Step 1:**Disconnect all the external devices (printers, scanner, USB (universal serial bus) drives, etc...) Including the drive in question, except mouse and the keyboard and then boot up
If this corrects the issue then add the devices back one at a time until you discover the piece of hardware causing the issue. Then get any updated drivers\software for the device.
For more details on updating drivers, clickhere
Step 2: Boot the computer in safe mode and check if the issue persists, to do this, follow the steps below,
Access the advanced boot options menu by turning on your computer and pressing the F8 key before Windows starts. On the advanced boot options menu select safe mode
http://windows.microsoft.com/en-US/windows-vista/Advanced-startup-options-including-safe-mode
If the issue doesn’t persists in safe mode you can infer that the issue could be driver or software related.
Thanks and Regards:
Ajay K
Microsoft Answers Support Engineer
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