○ Unable to install Modem

Have you been trying to install modem drivers and unable to succeed?

Here are three suggestions to fix the issue:

Windows 2000/XP has a bug that it cannot properly detect new hardware by *.inf files, if the RunOnce registry key is missing for the following location:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion

This key is often used by installers to execute post-reboot programs, but sometimes they accidentally delete this key.

IMPORTANT: This article contains information about modifying the registry. Make sure that you understand how to backup and restore the registry, in case a problem occurs. Please read the linked Microsoft Knowledge Base article prior to editing the registry.


Go to Start » Run and enter "regedit."

Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion

With CurrentVersion Highlighted, go to the Edit menu and select New » Key

Name the key RunOnce, leaving everything else about the key alone.

The RunOnce key should now exist underneath the CurrentVersion key.
Once the key exists, Windows 2000/XP stops redetecting the Hardware


If the solution above didn't work, copy the file "modem.sys" to C:\WINDOWS\system32\drivers and try again.

If it still doesn not work this will:

Copy your ".sys" file that came with your modem to C:\WINDOWS\system32\drivers
example: gtusbmdm_gpc6400.sys
Right-click the ".inf" and choose install.
Finally, in the device manager, your modem as a yellow "!" mark on it, perform a driver update and the modem will install.