Fax machine troubleshooting method in Vista

        When attempting to send or receive a fax using Windows Fax and Scan in Windows Vista, the transfer process may not complete after the connection is established.
Fault Cause
This issue may occur if one of the following conditions is true: • There is line noise on the telephone line connected to the modem.
• The modem has an abnormal behavior.
• A timing issue has occurred between the computer and the modem.
Warning: Serious problems can occur if you modify the registry incorrectly by using Registry Editor or by other means. These issues may require reinstallation of the operating system to resolve. Microsoft cannot guarantee that these issues will be resolved. Modifying the registry is at your own risk.
Workaround
To resolve this issue, you must use different class support to retransmit the fax. To do this, follow these steps:
1. Click Start, type device manager in the Start Search box, and then click Device Manager in the Programs list.
2. Expand Modem, right-click the modem you are using, and then click Properties.
3. On the Diagnostics tab, click Query Modem.
4. In the "Command" column, find "AT+FCLASS=?" and note the value in the "Response" column.
Note: If the value contained in the Response column is "1", "2", or "2.0", then the modem supports Class 1, Class 2, and Class 2.0, respectively.
5. Click Start, type regedit in the Start Search box, and then click regedit in the Programs list.
6. Locate and then click the following registry subkey:
HKEY_LOCAL_MacHINE\\Software\\Microsoft\\Fax\\TAPIDevices
7. Expand TAPIDevices and click the device ID of the modem.
8. Click Modem, right-click FixModemClass, and then click Modify.
9. In the Value data box, type one of the following values, depending on the class you want to set: • Type 1 to set the fax modem to use class 1
• Type 2 to set the fax modem to use the class 2
• Typing 20 sets the fax modem to use Class 2.0
10. Exit the Registry Editor.
11. Restart the fax service. To do this, click Start, type the service in the Start Search box, and then click Services in the Programs list.
If you are prompted for an administrator password or for confirmation, type your password or click Continue.
12. In the Services list, click Fax, and then click Restart.
13. Try to send a fax. If this problem occurs again, repeat steps 1 through 12 and set the modem to use a different class.