I'm a bit confused, originally I thought we were talking about files that had a .wps extension and now we seem to be talking about files with a .doc extension.
If the files have already been converted and saved with a .doc extension try the built-in wordpad application within Win7 and see if that will open them.  If on the other hand you have just renamed and changed that .wps extension to .doc, then you will need to change it back to .wps, open them using the works suite software on the other computer and resave them using the save as dialog box and choosing the .rtf extension from the drop down it's probably important to note that in doing this some formatting of the document may be lost with the new extension, but the general overall...