Why is Vista ".zip"ing all my Word files?

Just got a new laptop that’s running Vista, and when I try to save/send Word files, they’re coming up as .docx, instead of .doc, and are being automatically compressed. Now nobody that’s getting them can open them, nor can I.
...and they’re files that aren’t nearly large enough to need to be ”.zip“ed. (17 pages of text, for example)
It should be noted that I’m not very tech-savvy