It's a Dell SFF. All 6 screws have been removed. There are no other screws to remove. The heatsink, connectors, and everything on the motherboard have been removed/disconnected. The motherboard moves freely over the other screw holes except one in the corner where there is an audio jack close by. There is no screw in this hole and yet it won't move a millimeter. I've tried lifting the motherboard, wiggling it, pulling on the other connectors that are in the I/O panel to try and get it loose. Nothing works. It's like it's glued to the case.