DOCUMENT:Q150164  27-JUL-2001  [win95x]
TITLE   :VFBACKUP Could Not Load VFD.VXD
PRODUCT :Microsoft Windows 95.x Retail Product
PROD/VER:WINDOWS:95
OPER/SYS:
KEYWORDS:kbenv kberrmsg kbhw diskmem win95 kbHardware kbDiskMemory

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The information in this article applies to:

 - Microsoft Windows 95 
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SYMPTOMS
========

When you start your computer, you may receive the following error message:

   VFBACKUP could not load VFD.VXD

CAUSE
=====

The error message can be caused by one of the following:

 - SCSI controllers

 - Controllers that incorrectly assume maximum total physical memory of 16
   megabytes (MB)

 - Controllers that use their own DMA controller (as opposed to one of the
   pre-defined DMA channels on the system board) and whose BIOS lacks support
   for Virtual DMA Services (VDS)

 - A damaged or missing Vfd.vxd file in the Windows\System folder

RESOLUTION
==========

Follow these steps to enable double-buffering support for Windows 95:

1. At the MS-DOS prompt, type "attrib -r -s -h c:\msdos.sys" (without the
   quotation marks), and then press ENTER.

2. Type "edit c:\msdos.sys" (without the quotation marks), and then press ENTER.

3. Add the line "DoubleBuffer=1" (without the quotation marks) to the [Options]
   section of the Msdos.sys file, save the changes, and quit MS-DOS Editor.

4. At the MS-DOS prompt, type "attrib +r +s +h c:\msdos.sys" (without the
   quotation marks), and then press ENTER.

5. Restart the computer.

If following these steps does not resolve the behavior, repeat steps 1-5, and
change the line in the Msdos.sys file to DoubleBuffer=2.

NOTE: If your boot drive is compressed, make sure you edit the copy of the
Msdos.sys file located on the host drive for drive C.

If the Vfd.vxd file is missing or damaged, extract a new copy from your original
Windows disks or CD-ROM to the Windows\System folder. For information about
extracting a new copy of a file, please see the following article in the
Microsoft Knowledge Base:

   Q129605 How to Extract Original Compressed Windows Files

MORE INFORMATION
================

If Windows Setup determines that your controller may need double- buffering, it
will add a DoubleBuffer=1 (or 2) entry to the [Options] section of the Msdos.sys
file, which will automatically load Dblbuff.sys. To manually enable
double-buffering, you can either add the entry described in the "Resolution"
section to the Msdos.sys file, or add the following line to the Config.sys
file:

   DEVICE=<drive>:\<path>\DBLBUFF.SYS [/D+]

The optional /D+ parameter instructs Dblbuff.sys to double-buffer all disk I/O
all the time. By default, it will only double-buffer I/O to upper memory blocks
(UMBs), and it will automatically stop double-buffering if it appears to be
unnecessary.

Failures related to a need for double-buffering usually occur first during read
operations, but the computer may eventually write incorrect data to the drive
resulting in file corruption.

Additional query words: buffering doublebuffer

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Keywords          : kbenv kberrmsg kbhw diskmem win95 kbHardware kbDiskMemory 
Technology        : kbWin95search kbZNotKeyword3
Version           : WINDOWS:95
Issue type        : kbprb

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