Why it s confusing.
The WPS extension comes from Microsoft Works. This product was discontinued in 2010 and looks very similar to Word. many people get confused by this.
Way around it.
You can try using openoffice.org a free download that will work "seamlessly" with Office. I haven't tried it myself but feedback is positive.
If you can access your files you may want to try zamzar.com a free online converter.