Err Msg: Uninstall Is Unable to Write to the MBR

 Last reviewed: December 1, 1995
Article ID: Q139107
The information in this article applies to:
  • Microsoft Windows 95

SYMPTOMS

When you try to use the Uninstall option in the Add/Remove Programs tool, you may receive the following error message when your computer restarts: 

   Uninstall is unable to write to the MBR
When this occurs, the Uninstall procedure cannot be completed, and you may not be able to start the computer from the hard disk.

CAUSE

This problem can occur when any of the following conditions exists:

  • The hard disk's Master Boot Record (MBR) is damaged.
  • A software or hardware-level virus scanning program is protecting the MBR.
  • You are using third-party disk partitioning software.
  • You computer has been infected with a boot-sector virus.

RESOLUTION

Use the information in the appropriate section below to try to resolve the problem. If you cannot start your computer from the hard disk, you can start it using your Windows 95 Startup disk.

MBR Protected by Virus Scanning Software

If you suspect that a virus scanning program is preventing Uninstall from writing to the MBR, disable the virus scanning program by editing the Config.sys or Autoexec.bat file to temporarily disable the program. Place the word "Rem" (without quotation marks and followed by a space) at the beginning of the line or lines used to load the virus scanning program. After you make this change, restart the computer.

For information about the virus scanning program, consult the program's documentation or manufacturer.

MBR Protected by Hardware-Level Virus Scanning Program

To disable hardware-level virus detection, run your computer's CMOS configuration utility and disable the virus detection.

For information about your computer's CMOS configuration utility, please consult the computer's documentation or manufacturer.

Third-Party Partitioning Software

If third-party partitioning software is preventing Uninstall from writing to the MBR, refer to the software's documentation for information about restoring the previous MBR or modifying the current MBR.

Boot-Sector Virus

If you suspect that your computer has been infected with a boot-sector virus, use an anti-virus program to detect and remove the virus.

For additional information about viruses, please see the following article in the Microsoft Knowledge Base: 

   ARTICLE-ID: Q82923
   TITLE     : Methods to Detect a Boot-Sector Virus
After you resolve the problem that is preventing Uninstall from writing to the MBR, start your computer with your Windows 95 Startup disk, and then run Uninstall by typing the following command at the command prompt 

   <disk>:\uninstal <W95undo.dat_location>
where <disk> is the drive containing the Startup disk and <W95undo.dat_location> is the full path to the W95undo.dat file.

KBCategory: kbsetup kberrmsg
KBSubcategory: win95
Additional reference words: 95

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Last reviewed: December 1, 1995
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