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Troubleshooting Serial and Parallel Ports (Windows 98, ME, and XP)

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Use the steps in this document to fix serial and parallel issues by enabling, or resetting the serial and parallel ports.

Step 1: Enabling the ports in the BIOS

A parallel or serial port has to be enabled in the Basic Input/Output System (BIOS) before it can function properly. Many parallel devices also require that ECP mode be used. Use the following steps to enable the ports and ECP in the BIOS if they are disabled:
  1. Turn on the PC and press the F1 key repeatedly when the first screen appears. On some Presario PCs the key to enter setup may be F10.
  2. Press the RIGHT ARROW key to select the Advanced menu screen.
  3. Use the UP and DOWN ARROW keys to select I/O Device Configuration and press the ENTER key.
  4. Use the UP and DOWN ARROW keys to select the listing next to Serial Port A.
  5. If it is not already set to Enabled, press ENTER to select Enabled.
  6. If the listings next to Base I/O Address and Interrupt Request (IRQ) for Serial Port A is the same as the listing for Serial Port B, then select the Base I/O Address number and change it to a different number. The default numbers for most computers are 3F8H/IRQ 4 for serial port A and 2F8H/IRQ 3.
  7. Select and enable Serial Port B and the other Parallel ports in the same way.
    NOTE: There is a mode setting for the parallel port. Many parallel scanners and multifunction devices do not work unless this mode is set to Extended Capabilities Port (ECP) mode. Enter Mode and make sure that this is set.
  8. Press the F10 key to save the settings and exit.
  9. Connect a serial or parallel device to test the serial or parallel port. If the serial or parallel device fails, go to the next step.

Step 2: Reinstall the ports

Remove and reinstall the serial or parallel ports to force Windows to reset the information for the ports. When Windows discovers the ports again it will look for open IRQ numbers and re-assign a new IRQ and Base Address for the port. Use the following steps to remove and reinstall the ports in Windows:
  1. Restart the PC and press the F8 key repeatedly, every second, until a menu is displayed.
  2. Select Safe Mode and press the ENTER key. Windows will open with Safe Mode displayed in the corners of the desktop.
  3. Right-click the My Computer icon, and click Properties.
  4. In Windows XP, click the Hardware tab and then click Device Manager.
    In Windows 98 and Me, click the Device Manager tab.
  5. Click the plus (+) sign next to the Ports (COM & LPT) device.
  6. Right-click a serial or parallel port, and then click Uninstall or Remove.
  7. Click OK to confirm the removal of the port.
  8. Continue removing the ports until all serial ports or all parallel ports are removed.
  9. Restart the PC.
  10. When Windows opens, it automatically finds and configures the ports.
  11. Connect a serial or parallel device to test the serial or parallel port. If the serial or parallel device still fails, then try the following items:
    1. Use a different cable to connect the device.
    2. Use a different port to connect the device (serial).
    3. Check the Web site or documentation for the device that is using the port. The device may require special settings in order to operate correctly.
    4. If an extra parallel card was installed, make sure that the hardware jumpers on the card are set to different IRQ and Base I/O Address numbers than those used by LPT1 in the BIOS. Refer to the documentation that came with the card or card manufacturer's Web site.
    5. Remove support for serial key devices from Windows accessibility options, if you are not using any serial key devices:
      1. In Windows XP, click Start, and then Control Panel.
        In Windows 98 and Me, click Start, Settings, and then Control Panel.
      2. Double-click Accessibility Options and then click the General tab.
      3. In Windows XP, remove the checkmark from Use Serial Keys if necessary and click OK.
        In Windows 98 and Me, remove the checkmark from Support SerialKeys devices, and click OK.

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