Microsoft Word is part of the MS Office Suite.
Microsoft Works is a slimmed down suite offered by MS for free on many computers.
They have different file formats and need converters to open files.
Convert Works documents to Word format:
By using a file format converter in Microsoft Word, you can open documents that were created in Microsoft Works. After you open the document, you can save it in Word format.
1. On the File menu, click Open.
2. In the Files of type list, click Works 6.0 & 7.0.
If you don't see this option in the list
3. In the File name box, enter the name of the file that you want to convert, and then click Open.
4. On the File menu, click Save As.
5. In the Save As dialog box, make any changes that you want in the File name box, click the file format that you want in the Save as type list, and then click Save.
(From Microsoft instructions)