Microsoft generally makes newer programs backward-compatible with their older versions, so they can at least read the old program’s files. But in Windows XP SP2, the file converters for old versions of WordPad files aren’t enabled by default. If you don’t have Microsoft Office installed, WordPad is the default application for opening DOC and RTF files – and it can’t handle the old ones. With Office installed, Microsoft Word takes over, and it will successfully open old DOC and RTF files. But even then, WordPad remains the default application for files with the WordPad-specific WRI extension.
Fortunately, a simple Registry tweak will enable Win XP SP2’s WordPad to read these files.
Launch Regedit from the Start menu’s Run dialog and navigate to the key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ Applets\Wordpad.
In the right-hand pane look for a DWORD value named EnableLegacyConverters. If it’s not present, right-click in the right-hand pane, choose New | DWORD Value from the menu, and name the value EnableLegacyConverters.
Double-click that value and change its data from 0 to 1. You might have to restart Windows for this change to be recognized.