time961 writes "In Service Pack 3 for Office 2003, Microsoft disabled support for many older file formats. If you have old Word, Excel, 1-2-3, Quattro, or Corel Draw documents, watch out! They did this because the old formats are 'less secure', which actually makes some sense, but only if you got the files from some untrustworthy source. Naturally, they did this by default, and then documented a mind-bogglingly complex workaround (KB 938810) rather than providing a user interface for adjusting it, or even a set of awkward 'Do you really want to do this?' dialog boxes to click through. And of course because these are, after all, old file formats ... many users will encounter the problem only months or years after the software change, while groping around in dusty and now-inaccessible archives."