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

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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

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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, and then press ENTER.
2.	Type edit c:\msdos.sys, and then press ENTER.
3.	Add the line DoubleBuffer=1 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, 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:

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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: 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.

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