of the Windows Registry Checker Tool (Scanreg.exe)
When you start your
computer successfully, the Windows Registry Checker tool (Scanreg.exe) creates
a backup of system files and registry configuration information (including user
account information, protocol bindings, software program settings, and user preferences)
once daily. Files that Windows Registry Checker backs up include System.dat, User.dat, System.ini,
and Win.ini. This article describes the Windows Registry Checker tool.
Checker automatically scans the system registry for invalid entries and empty
data blocks when it is started. If invalid registry entries are detected,
Windows Registry Checker automatically restores a previous day's backup. This
is equivalent to running the scanreg /autorun command from a command prompt. If no backups are
available, Windows Registry Checker tries to make repairs to the registry. This
is equivalent to running the scanreg /fix command
from a command prompt. If the registry contains more than 500 KB of empty data
blocks, Windows Registry Checker automatically optimizes it.
Windows Setup runs the
Windows Registry Checker tool to verify the integrity of the existing registry
before it performs an upgrade. If it detects registry damage, it tries to fix
version of the Windows Registry Checker tool (Scanregw.exe) can create a backup
of the system files and scan the registry for invalid entries. If invalid
entries are detected, it refers to the real-mode version of the Windows
Registry Checker tool (Scanreg.exe) for a resolution.
You can configure
Windows Registry Checker with a Scanreg.ini file. Settings that you can
or disabling the tool
number of backups maintained (no more than five is recommended)
location of the backup folder
to add additional files to the backup set
information about the Scanreg.ini file, click the article number below to view
the article in the Microsoft Knowledge Base:
183603 How to
Customize Registry Checker Tool Settings
To start the Windows
Registry Checker tool, click Start, click Run, type scanregw.exe in the Open
box, and then click OK.
NOTE: To use the
Windows Registry Checker tool with the /restore parameter, you must run the
tool from a command prompt running outside of Windows. When you do so, you can
choose up to five registry backup files listed for you to restore.
To Restore Individual
To restore individual
files, follow these steps:
1. Click Start, point to Find, and then
click Files Or Folders.
2. In the Named
box, type rb0*.cab, and then click Find Now.
3. Double-click the cabinet file that
contains the file that you want to restore.
4. Right-click the file that you want to
restore, click Extract, and then choose the folder where the new file is to be
placed. Microsoft recommends that you place the file in your Temp folder.
5. Restart your computer in MS-DOS mode (in
Windows Millennium Edition, this requires that you restart with the Windows
Millennium Edition Startup disk).
6. Copy the file that you extracted to the
appropriate folder. Note that registry .dat files are
typically marked as hidden and read-only, so you need to use both the attrib
and copy commands to replace the existing file with the newly extracted one.
Known Issues for
Windows Registry Checker
If your registry
contains an entry that references a file (such as a .vxd file) that no longer
exists, it is not repaired by Windows Registry Checker. Such errors are not
typically damaging, and you can manually remove the entry. For additional
information about such errors, click the article number below to view the
article in the Microsoft Knowledge Base:
The amount of
conventional memory that is required by Windows Registry Checker is determined
by the size of your registry. Windows Registry Checker may require 580 KB or
more of free conventional memory to complete the repair process. If you
encounter an "Out of Memory" error message, optimize your free
conventional memory. For additional information about optimizing memory, click
the article number below to view the article in the Microsoft Knowledge Base:
NOTE: Extended memory
is required for Windows Registry Checker to operate properly, so it does not
run when you start your computer with the Safe Mode Command Prompt Only option.
The exception to this is the scanreg /restore
command, which is the only Scanreg function that can
run without extended memory memory