Microsoft KB Archive/843617

= You cannot adjust your portable computer's LCD display contrast or backlight controls in Windows XP =

Article ID: 843617

Article Last Modified on 5/15/2007

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APPLIES TO


 * Microsoft Windows XP Professional
 * Microsoft Windows XP Home Edition

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SYMPTOMS
When you use Microsoft Windows XP on a portable computer, you may not be able to adjust the contrast or the backlight controls on your LCD display. Additionally, CreateFile function calls to open the \\.\LCD device may return an &quot;ERROR_FILE_NOT_FOUND&quot; error message. This problem may occur when the following conditions are true, in the order that they are presented in:
 * You start your portable computer without a connected CRT monitor.
 * You connect a CRT monitor to your portable computer.
 * You switch the display from the portable computer LCD display to the CRT monitor, and then you switch it back to the LCD display.



CAUSE
This problem is caused by a conflict in the video port component of Windows XP that occurs during the enumeration of the Advanced Configuration and Power Interface (ACPI) devices that are connected to the computer. ACPI devices are display devices such as LCD displays or CRT monitors.



Service pack information
To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

Hotfix information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows XP service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

File information
The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

Windows XP, 32-bit editions
  Date         Time   Version        Size    File name -  18-Jun-2004  18:14  5.1.2600.1545  71,168  Videoprt.sys

Windows XP, 64-bit editions
  Date         Time   Version        Size     File name --  18-Jun-2004  18:14  5.1.2600.1545  284,800  Videoprt.sys



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section. This problem was first corrected in Microsoft Windows XP Service Pack 2.



MORE INFORMATION
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbqfe kbhotfixserver kbwinxpsp2fix kbwinxppresp2fix kbfix kbbug KB843617

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