Windows 95/98
Check if the GSM 6.10 codec is installed
Click on "Start -> Settings -> Control Panel -> Multimedia".
Now click on the "Devices" tab, and then open "Audio Compression Codecs".
Check if "Microsoft GSM 6.10" appears in the list.
Installing the GSM 6.10 codec
On the Control Panel, click on "Add New Hardware".
Click "Next", choose "No" and click on "Next" again.
Select "Sound, Video and Game Controllers" and click on "Next".
Select "Microsoft Audio Codecs" on the left, and then "GSM 6.10"
Click on "Next", and then "Finish".
Windows 2000/XP
Check if the GSM 6.10 codec is installed
Click on "Start -> Settings -> Control Panel -> Sounds and Multimedia".
Now click on the "Hardware" tab, and then double-click on "Audio codecs".
Click on the "Properties" tab, and check if "Microsoft GSM 6.10"
appears in the list.
Installing the GSM 6.10 codec
Click on "Start -> Settings -> Control Panel -> Add/Remove hardware".
Click "Next", select "Add/Troubleshoot a device" and then "Next" again.
There will be a short delay while Window searches for devices
Select "Add a new device" and click "Next".
Select "No, I want to select the hardware from a list", and click "Next".
Select "Sound, video and game controllers", and click "Next".
Click the "Have Disk..." button.
Browse to "C:\WINNT\system32\mmdriver.inf" and click the "Open" button.
A window with the message "Digital signature not found", click "Yes".
Select "Microsoft GSM 6.10 Audio CODEC" and click "Next".
A confirmation window will appear, click "Next".
You may get the warning about "Digital signature not found" again. Click
"Yes" if it does.
Once it has installed the codec, click "Finish".