Microsoft KB Archive/186057

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Article ID: 186057

Article Last Modified on 1/23/2007


  • Microsoft Windows Millennium Edition
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows 98 Standard Edition
  • Microsoft Windows 95

This article was previously published under Q186057

If this article does not describe your hardware-related issue, please see the following Microsoft Web site to view more articles about hardware:


This article describes how to determine if a drive overlay program is running on your Windows-based computer.


A drive overlay program is provided by third-party manufacturers and is loaded into memory before your computer's startup system files are loaded. A drive overlay program may be installed for any of the following reasons:

  • Your computer does not support logical block addressing (LBA). This may be because the Basic Input/Output System (BIOS) of your motherboard does not support hard disks that are larger than 528 megabytes (MB).

    For information about LBA, see the following article in the Microsoft Knowledge Base:

    ARTICLE-ID: 122052
    TITLE : Logical Block Addressing (LBA) Defined

  • Your computer has a hard disk that is larger than 1024 cylinders or 4096 cylinders.
  • Your computer has incompatible hard disk drives that need to be used together.

The following methods may or may not detect if a drive overlay program exists on your Windows-based computer. If you are uncertain if a drive overlay program is installed, contact your motherboard manufacturer or hard disk manufacturer. To determine if a drive overlay program is installed, use any the following methods:

Drive Overlay Message

When you start your computer, a message may be displayed on the screen that displays the manufacturer's name or prompts you to press a key to boot to a floppy disk. Current versions of drive overlay programs may not display this message by default.


Computers made before 1994 do not support LBA. To verify if the BIOS on your computer supports LBA, consult the manufacturer's documentation or contact the manufacturer of your computer.

Fdisk Status Command

Start your computer with the Windows 95/98 Startup disk, type "Fdisk /status" (without quotation marks) at the command prompt, and then verify that the sum of the existing partitions is larger than the total hard disk space.

Windows 95/98 Startup Disk

Turn off your computer, wait 10 seconds, start your computer with the Windows Startup disk (this prevents the drive overlay program from loading), and then boot to a command prompt. Compare the date and size of system files in the Windows folder for minor inconsistencies. If the physical disk size is much greater than 528, type "c:" (without quotation marks), and then press ENTER. Type cd \windows\command to determine if it is accessible.

NOTE: This only applies if this subfolder was created after the first 528 MBs are filled.

Verify Files

Some drive overlay files use an .ovl or a .bin extension. At the command prompt, type "Dir /a *.bin" or "Dir /a *.ovl" (without quotation marks) to check for the existence of files other than drvspace.bin and dblspace.bin.

Check Config.sys

Drive overlay software may be loaded from the Config.sys file to access drives other than the active boot partition of the master drive on the primary IDE controller.

Memory Check

Boot to command prompt only, and then test your computer's memory. To do so, use the following steps:

  1. Restart your computer, and press F8 when you see the "Starting Windows 95" message.
  2. Choose command prompt only, and then press ENTER.
  3. At the command prompt, type "MEM /C" to determine the total amount of conventional memory. A number less than 655,360 may indicate the existence of a drive overlay program, however a lesser number may instead indicate the existence of a SCSI drive or Master Boot Record virus.

NOTE: Many recent versions of drive overlay software do not use conventional memory.

Additional query words: HWDDRV invalid media type dir directory missing windows

Keywords: kbenv kbfaq kbhowto KB186057