Why can't I delete this file?

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Summary: Sometimes a file cannot be deleted because it has invalid characters in its filename. There are techniques and tools to force the delete anyway.

It's a fact that you can create files in Windows that are almost impossible to delete using normal methods. Typically it's the result of a hidden character in the filename - a character that for various reasons can't be seen and is difficult if not impossible to type. And yet if you don't specify the correct filename including that odd character you can't delete the file.

I can hear you asking "great, how did that character get there and more importantly how can I delete the file?"

The answer to the first part is speculation but I was recently pointed at a tool that will help with the second.

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The biggest issue with invalid names is that not all programs filter out invalid characters from filenames before they pass them on to the system. For example, let's say you happened to accidentally hit the spacebar after the filename when you went to save a file. If the application you're using is not smart enough to strip trailing spaces then it may well create the file with a trailing space. You may think and see "FOO.DOC", but Windows sees "FOO.DOC ". A subtle, but important difference.

What's worse is when you attempt to rename the file or delete the file using a utility that then "does the right thing", it strips trailing spaces before it attempts to operate on the file. You type in or select "FOO.DOC " with a space and the utility takes it as "FOO.DOC" without a space, tries to delete it, and fails because that's not the name of the file!

There are actually several scenarios that can result in files that seem almost impossible to delete. Fortunately they are rare but they do happen.

What to do?

If your file system is FAT or FAT32 or most instances of NTFS you can use the old DOS "shortname". In the days before Windows filenames under MS-DOS could only be 11 characters long. For compatibility with old programs that relied on the 11 character limitation Windows creates a unique "shortname" for every long file name. For example, if your file is named "thisisalongfilename.isntit" a DIR /X in a command shell may show the shortname as "THISIS~1.ISN". It refers to the same file so you can delete using the shortname.

In some cases using the command shell or using shortnames isn't an option. That's a situation I found myself in some time ago. My disks are formatted with NTFS, and I've explicitly turned off "shortnames" for a little bit more speed. I had no way to delete the file I'd somehow created.

I was recently pointed at delinvfile, short for Delete Invalid File, from Assistance & Resources for Computing, Inc. It's a free Windows program that uses standard controls for drives, folders, and files to navigate to the folder and to select the file to be deleted. Push a button and it's gone.

It just got added to my little arsenal of handy tools I carry with me wherever I go.

Article C1907 - March 15, 2004

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