As Jo mentioned, downloading a converter program from Microsoft will not only take care of the .wps files but the .docx vs .doc files as well.

This trick was discovered when one of the client's I type for brought a file home, did some editing in Office 2007, and couldn't open it back up when she got to work. She asked if I could do it and after doing some research, I downloaded the converter from Microsoft and was able to open the file up and saved it as a .doc file. We have not had the problem since. I gave her the link to download the converter and it has been working out well for them.