To test a modem
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.
Open Phone and Modem Options in Control Panel.
On the Modems tab, click the modem you want to test.
Click Properties, click Diagnostics, and then click Query Modem.
To open Phone and Modem Options, click Start, click Control Panel, and then click Network and Internet Connections. Under See Also, click Phone and Modem Options.
This procedure sends standard AT commands to your modem, and displays the responses that indicate features supported by your modem.