This is a used projector and it works great except when I try to run a computer off of it.

I get a black box artifact on the screen as seen here

It happens regardless of what computer I use, what connection I use (M1, vga), resolution, nothing makes a difference....

Video signals from other sources work perfectly.
Any ideas?

Figured it out. Somehow PIP got turned on when the computer connectiosn. I just got this projector so I didn't know it had PIP