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Registry Tools and Root Keys

The Windows Registry

(Windows 98/ME/2000/XP)

If you need to amend the Windows Registry always make sure that you back up your Registry settings before proceeding. To do this click START/RUN and type SCANREG. This starts the Windows Registry Checker which checks for any errors - if there aren't any, it asks you if you want to backup the Registry again. Accept the offer!

Windows 98 and ME back up the registry at Start Up once a day and by default keep the last 5 working copies. To increase the number of copies kept you must edit the C:\WINDOWS\SCANREG.INI file by changing the MaxBackupCopies value from 5 to whatever you want it to be.

Once the backup is complete click START/RUN type REGEDIT and press ENTER. Now you are confronted with a list of Registry Root Keys:


This Key stores file associations and related information.


This Key stores the individual preferences for all the Users on your PC. This is mostly the contents of USER.DAT (located in the Windows folder).


This is just the section of HKEY_USERS for whoever is using the PC at the time.


The Key stores information about hardware, software and preference from SYSTEM.DAT (located in the Windows folder).


This links to the section of HKEY_LOCAL_MACHINE for the current hardware configuration of primarily graphic cards and printers.

HKEY_DYN_DATA (not used by Windows XP)

This key stores information about Plug and Play devices.

If you delete old Keys for the packages you've perhaps uninstalled and you use Windows 98 or ME, you can compress the Registry to improve its performance (this is automatically done in Windows XP). Restart your PC in MS-DOS mode and run SCANREG /OPT to remove unused space and shrink the file sizes.

Fixing Registry Problems

If there is a problem with the Registry, for example after it's been amended in some way, Windows Registry Checker replaces it with the most recent backup copy.

To force Registry Checker to use an older version press F8 as Windows boots up and chose Safe Mode Command Prompt. At the C:\ prompt type SCANREG/RESTORE and chose which backup to choose.

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