That display problem is a symptom of incorrect CMOS settings usually caused by a dead battery. Sometimes you can change the display resolution parameter in the Power parameters to 640x350 and see the entire screen.
To try it, you will need to press the buttons even though you can't see them.
Try this: after you power the machine up and you see the partial display, press F7-F1-F1.
Key in the password PROTO3 and press enter, then press another 3.
Now press F9 and the screen should go black. The next step depends the age of your machine.
If this is an older simdisk machine, key in a:\cnc\cnc /v0 (foreslash v zero)
If this is a newer single board computer machine, key in c:\cnc\cnc /v0
If this works, get back to level 3 and change the Power patameter.
The error on the drive should go away when you reset the machine.