A family of Microsoft word processing software products for creating web, email, and print documents.
Yes, you are opening the wrong "half" of the file.
A Mac file is in two parts, for historical reasons. There is nothing in the first half, but it's still written, for compatibility purposes.
Windows File Explorer can be set to show and manage as a single file, to show both but manage as a single, or to show and manage both parts separately.
You just need to make yourself a mental note to check the file extension when opening on Windows (or the size... the blank part is only 245 bytes...)
Better yet: Get out of the habit of "opening" files on a Flash Drive. Copy them to your hard drive first. There are a variety of "bad things" that can happen if you try to edit Word files on flash drives, better not to tempt fate.
Cheers