A wps file was created by Microsoft Works, so it's particularly annoying when other Microsoft programs don't recognise it!
If it was created in Works 6.0 or 7.0 you can use Microsoft Word Viewer to open it:
http://www.microsoft....f20cac&displaylang=en
If it was created in an older version Works, this converter should do the trick:
http://www.microsoft....f20cac&displaylang=en
It would probably still be easier to ask the writer to open the document, on their own computer, using Microsoft Works. They should then click on File > Save As.
From that list they should choose the most appropriate option. If the 'Word 97-2003 (*.doc)' option, or something similar, is present they should select that one. Otherwise they should select something like 'Rich text format (*.rtf)' or whatever else might be compatible with your own word processor. They can then send you the amended file.
Chris