Consider the following scenario:

• You have a Windows Vista-based computer that does not have an internal USB optical disc drive. Instead, an external USB optical disc drive is connected to the computer.
• You run an application that calls the AcquireExclusiveAccess routine in the Imapi2.dll file to exclusively use the optical disc drive on the computer.

In this scenario, you may notice that the external USB optical disc drive is removed from the Windows Vista operating system. When you reconnect the optical disc drive to the Windows Vista-based computer, the operating system does not recognize the optical disc drive. Additionally, a yellow exclamation mark (!) may appear next to the external USB optical disc drive in Device Manager. You may receive an error that resembles the following:

Error 38 (CM_PROB_DRIVER_FAILED_PRIOR_UNLOAD)

Note: The external USB optical disc drive can be displayed correctly in Device Manager after you restart the computer.