When you try to start Control Panel / Modems or Control Panel / Telephony.. / Unimodem.. / Configure, the hourglass flashes briefly but the dialogue box does not open.

If you try to open modem properties from a CMD prompt, it doesn't open:

control modem.cpl
rundll32.exe shell32.dll,Control_RunDLL modem.cpl

NOTE: The rundll32.exe commands are case sensitive.

Possible causes of this difficulty are:

1. Modem.cpl is missing or damaged. Expand it from the CD-ROM:

    expand \i386\modem.cp_ %SystemRoot%\System32\Modem.cpl

2. The %SystemRoot%\System32\Modem.cpl file doesn't have proper permission. Set the following permissions:

    Administrator - Full Control
    Everyone - Read
    Server Operators - Change
    SYSTEM - Full Control

3. A registry key/value is missing or damaged. Use Regedt32 to verify / fix:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\\{4D36E96D-E325-11CE-BFC1-08002BE10318\}

  Value Name: Installer32
  Data Type: REG_SZ
  String: Modem.Cpl,ClassInstall32

  Value Name: Icon
  Data Type: REG_SZ
  String: 0

  Value Name: Default Service
  Data Type: REG_SZ
  String: Modem

  Value Name: Class
  Data Type: REG_SZ
  String: Modem

  Value Name:
  Data Type: REG_SZ
  String: Modem