I just flashed the BIOS on my Asus P5W DH motherboard with a more current version (1901), using an 'Ezyflash' tool from Asus.

When I rebooted there was a message during start up that said 'CMOS values error'. Then another message 'Operating system missing', and nothing happens. I'm sure the OS is ok (Raid 5).

Anyone got an idea what the CMOS error means, and how to recover the system? There is another flash utility within the Bios itself, but it doesn't work.

Thanks.

Did you enter the Bios and then exit? Sometimes that might kick start things.

If you can get into the BIOS, then select the option to reset to defaults, sounds like the CMOS didn't get the info transferred from the flash rom. Another is the mainboard will have a place to hardware reset the CMOS, try that if the above doesn't work.

I guess you are using a raid 5 controller like these intel onboard ones which are quite popular nowadays, make sure the system is trying to boot of it.

I guess you are using a raid 5 controller like these intel onboard ones which are quite popular nowadays, make sure the system is trying to boot of it.

That fixed it. The problem was that the drives were no longer configured as a RAID in the new BIOS, I guess the setting had been overwritten. As soon as it was set to RAID it started working.

Thanks to all.