I have some Microsoft Word 5 files from 1990 that were not opening properly in Word 2013. I could see some text but not all, and the formatting was wrong.
This tip by Allen Wyatt helped me solve the problem. Unfortunately, the WDSUPCNV.EXE file is no longer available on the FTP site linked in that article. However, I went to an old computer where Word 2007 was installed, copied the file doswrd32.cnv to my current machine running Office 2013, and Word 2013 was then able to open Word 5 files.
On the old 32-bit Windows XP machine, that file was here:
\Program Files\Common Files\Microsoft Shared\Textconv
On my newer 64-bit Windows 7 machine, I put the file here:
\Program Files (x86)\Common Files\Microsoft Shared\Textconv