This is something I've never run across before.
Turn on the computer, it doesn't go through the POST or CMOS. Immediately: black screen, blue box, white lettering with the word "override".
Thinking the CMOS was permanently damaged, we replaced the motherboard, RAM and case. Used the same hard disk, floppy drive, CD-ROM and modem.
The "new" computer worked flawlessly, rebooted several times, etc. Came in this morning and it is doing the same thing. Black screen, etc.
I thought MBR virus, but then how could we use the old hard disk in a new system. Everything was there and worked with the new system until this morning. Also most viruses don't wait around for several boots to do their damage.
I have found NOTHING on the net to indicate what this problem is and how to solve it other than it involves the CMOS.