RegDelNull deletes undeletable Windows Registry keys

Serdar Yegulalp, Contributor

Windows administrators rely on the simplest and most common tools to get a job done for one simple reason -- because they work. For instance, REGEDIT isn't a sophisticated program, but if all you need to do is make one quick change to the Windows Registry, it will do the job just fine.

However, there are times when, because of a problem with the key you're working with, REGEDIT won't let you make that one quick change. One instance of this is when you try to delete a Registry key that has an embedded null character in its name.

(An embedded null is a character with a binary value of zero -- not something you can type from the keyboard most of the time, but you can certainly create it programmatically.) An embedded null can wreak havoc with Registry editors, since most of them are not programmed to recognize nulls in key names.

Some "undeletable" Registry entries are merely entries that have null characters. (The inability to delete them conventionally seems to be a quirk of the Win32 API, the programming interface used by most Windows applications. After all, the Native API used by the Windows kernel internally does recognize null characters in Registry entries.)

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RegDelNull,a utility written by Mark Russinovich of Sysinternals, a Web site for freeware, utilities, technical information and source code related to Windows NT/2000/XP/2003. This command-line utility lets you delete Registry entries with embedded nulls.

To use it, pass a Registry path as a command parameter (such as HKLM for HKEY_LOCAL_MACHINE), then provide an –s switch to tell the program to recursively search all Registry entries beneath it. As it finds each Registry entry with an embedded null character, it will prompt you to delete it. Each time the program finds a matching Registry entry, it prints the name with an asterisk (*) to denote where the null character is.

 

Serdar Yegulalp is editor of the Windows Power Users Newsletter. Check it out for the latest advice and musings on the world of Windows network administrators -- and please share your thoughts as well!

 

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This was first published in January 2006

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