I am like Grelber and assumed MS Office/Word were backward compatible. Apparently I was mistaken. I did some research on MS Office file compatibility (a tip of the hat to Wikipedia) but I do not claim my research is comprehensive. It appears that prior to Mac Office 4 (released sometime in the late 90's) the Mac versions of the MS Office applications did not use the same file format as the Windows versions. It wasn't until the release of Mac Office 4 the Mac version changed to the same file format used in Windows and since that time the files have been interoperable between the two platforms (with exceptions such as the omission of Visual Basic for Applications in the Mac version from Office 2008 until Office 2011). Apparently all of today's Mac apps are based on that common file format and not the older Mac Office 3 and previous format.
Joboy, I found an application called
Doxillion that purports to convert a host of different file formats into other file formats for both Windows and the Mac, but I didn't see any obsolete file formats that it purports to support.
Dataviz used to have a really great document conversion application called Maclink Plus that probably would have been able to convert your files to a more modern format, but it has been out of print for years. If you could find a copy on someone's dusty back shelves it would probably require a PPC processor to run.