I’m always getting files at work in DOCX format. For those of you who aren’t tech-savvy, DOCX format is something Microsoft invented to force everyone to upgrade their Microsoft Office Suite to add a bunch of features they don’t really need. Instead, I use Zamzar. It quickly converts DOCX into plain old DOC, which lets me get on with my work. It is also useful for other kinds of file conversions: images, video, music, etc., although I’ve never had occasion to use it for those purposes.
You can sign up for paid service, which gives you faster service, online storage, and no ads, but what they offer for free is sufficient for my needs.