When I try to open some very old Word documents (made with Word 2.0) in Word 2003 on Windows XP a message appears saying “You are attempting to open a file that was created in an earlier version of Microsoft Office. This file type is blocked from opening in this version by your registry policy setting”. I could not find a way to change this policy setting or an explanation of the implications of these changes. Can you advise?

It is useful that you have provided the version of Word that you are using to open the files (Word 2003) as that is crucial information for diagnosing this issue. Reading a Microsoft Knowledge Base article on the subject (support.microsoft.com/kb/922849) indicates that in the most recent versions of Word (2007 and 2010) documents from Word 1.0 and 2.0 (amongst other versions of Word as well) are no longer supported and will not open. However, Word 2003 should still support opening these documents, but it is possible for a computer administrator to block the opening of particular types or versions of files in Word 2003. This is usually used in a corporate environment where the IT policy may dictate that particular file types cannot be opened, perhaps due to security reasons or for standardisation reasons, but this should not be an issue on a home computer so it begs the question as to why these file types are being blocked.

Further research on the topic found a blog post on the MSDN (Microsoft Developer Network) by David LeBlanc, one of the developers involved with the Office family of products. The blog post is available at blogs.msdn.com/b/david_leblanc/archive/2008/01/04/office-sp3-and-file-formats.aspx . The article explains that the ability to restrict the reading of older file formats is for security, as the parsers that were written to read these older types of files are not as robust as more recently written parsers, potentially creating security risks. When Service Pack 3 for Office 2003 was released, the file formats which could be opened by default were changed and restricted to assist in this tightening of security, which would explain why you were able to previously open the files (pre-SP3) but since the update was applied it no longer works correctly. Fortunately Microsoft has provided a way to reverse this behaviour so that you can open these older file types. At the bottom of the blog post you will see a listing of .reg files which allow you to enable (or block) the opening of file formats in the various Office applications. Before proceeding any further make sure that you close Word and any other open Office applications. Then download the “UnblockWord.reg” file from the MSDN blog post page to a location on your computer. Once the download has finished, find the file on your computer and double-click to open. A message will appear asking whether you wish to install the file – click “Yes”. A confirmation message will then appear indicating that the file has been successfully installed into the registry. Once this has happened try to open a Word 2.0 file and it should work correctly.

In case you are interested, the .reg file downloads are also available from a Microsoft Knowledge Base article at support.microsoft.com/kb/938810. Also on the Knowledge Base article are several other methods which you could alternatively use to re-enable the file types, although these are probably not particularly useful in your situation (and are more geared towards enterprise IT environments which need to deploy this fix across an entire environment) since the .reg fix should work fine for you.