At the boot process, is there any setting in the CMOS (or elsewhere) which can check on the integrity of the MBR BEFORE the MBR is loaded ? I have heard of applications which can check that the MBR is OK before executing the IPL code in the MBR. If the MBR is not OK the application can change it into a "known good" copy stored elsewhere on the disk and then boot from it. But is this possible ? How ?

The BIOS would have to support that feature. Go into the setup by hitting whichever key you have to hit (usually del, F1, or F2) when your computer first boots and see if you have anything in the menu about checking the MBR. If not, I don't believe it would be possible on that computer without changing out the BIOS. I could be wrong on this, but I seriously doubt that any kind of 'application' would be able to execute machine level code immediately following POST and before reading the MBR. That's pretty much a hard-wired area left to the ICs on the motherboard.

I am sure there are systems which store flash copies of the MBR (not your average PC). That said, the whole boot sequence is a chain and it is very hard to step back in the chain to fix anything (or look too far ahead). It is in fact in the best interests of everyone (including hackers and virus writers) to leave the MBR alone - the more abstract components of the OS are far easier to hide within and manipulate. Corruption is rare. The applications you have heard of most likely implement a simple step-through precedure, which a lot of systems (especially older ones) performed and reported on screen. This ensures that the MBR is ordered properly, and if an OS is found, the BIOS prints OK. Norton DiskDoctor can be set to run through the MBR and partition tables. Other than that, there are anti-virus programs which check the MBR at boot.

Some Amibios have a trend chipaway virus scanning chip built into it. However it puzzles me why you want to scan mbrs from bios, any decent antivirus will check the integrity of your mbrs on boot.

Hylain_lynk has a very good point. There really is no need to scan your MBR from the BIOS. I mean, your system is either going to boot or its not. Get a CD burner and make backup CDs of your hard drive's contents. That way you can sleep better at night and stop worrying about boot sector viruses. If you don't back up your important data, someday your hard drive is going to fail, virus or not, and then the computer tech is going to tell you that he has no choice but to FDISK your drive and reformat it. Save yourself a lot of trouble.