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How to Tell If Drive Overlay Program Is Installed in Windows

This article was previously published under Q186057
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This article describes how to determine if a drive overlay program isrunning on your Windows-based computer.
A drive overlay program is provided by third-party manufacturers and isloaded 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 programexists on your Windows-based computer. If you are uncertain if adrive overlay program is installed, contact your motherboard manufactureror hard disk manufacturer. To determine if a drive overlay program isinstalled, use any the following methods:

Drive Overlay Message

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


Computers made before 1994 do not support LBA. To verify if the BIOS onyour computer supports LBA, consult the manufacturer's documentation orcontact 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 verifythat 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 theWindows Startup disk (this prevents the drive overlay program fromloading), and then boot to a command prompt. Compare the date and size ofsystem files in the Windows folder for minor inconsistencies. If thephysical disk size is much greater than 528, type "c:" (without quotationmarks), 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 commandprompt, type "Dir /a *.bin" or "Dir /a *.ovl" (without quotation marks) tocheck 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 accessdrives other than the active boot partition of the master drive on theprimary IDE controller.

Memory Check

Boot to command prompt only, and then test your computer's memory. To doso, 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.
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Article ID: 186057 - Last Review: 01/23/2007 15:47:19 - Revision: 2.1

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