On Windows, what could be creating these strangely named, locked versions of .doc files?

they look indeed like MS Word temp files, to find out what's locking them, you may use this:

LockHunter is a foolproof file unlocker.

It is a tool to delete files blocked by something you do not know. LockHunter is useful for fighting against malware, and other programs that are blocking files without a reason. Unlike other similar tools it deletes files into the recycle bin so you may restore them if deleted by mistake.

Key Features

Shows processes locking a file or folder

Allows to unlock, delete, copy or rename a locked file

Allows to kill locking process

Allows to remove locking processes from hard drive

Integrates in to Explorer menu

It deletes files into the recycle bin, so you may restore them if deleted by mistake

Supports both 32 and 64bit Windows

LockHunter is freeware.

Microsoft Word creates a mess of temporary files in a document's directory when one is open. It could be possible that a crash would keep them locked. Try using Unlocker to unlock the files and then delete them.

Is word running? They look like temp files.