Opening old Microsoft Office files from years ago

This is the first time I have hit upon the problem (in a professional business context) of opening an older file in a newer application.

Specifically the file is listed under its properties as "Microsoft Word 5.0/5.1 for Macintosh Document" and I am using Microsoft Word 2003 SP3

It appears that SP3 for Office 2003 and I believe as standard in Office 2007 will not open file types earlier than Office 97 versions by default.

So the message you get when opening such a file under this configuration is

"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. "
http://support.microsoft.com/default.aspx/kb/922849

The fix was to correct the registry setting following the advice at MS support here
http://support.microsoft.com/kb/938810

And all is well - but clearly there is a business need to have access to files prior to 1997 both for historical, informational, reference purposes let alone the statutory obligations if applicable.

I am tempted now to make a new set files to sit alongside the originals in PDF format for future preservation.