*.dwg

???

Need additional detail. It sounds as if the files magically changed their extensions.

Was it every file in a specific directory that changed?
Did it occur after a specific event (IE software installation)?
Is ProE now saving files with a different extension?

Recneps

All files, all directories. I didn't a specific event.
Pro/e define drawing files with *.drw in my Pro/e Help
System.