This is probably a dumb question, but I haven't found anything that clearly describes what I need.

My system has 2 IDE (PATA) hard drives and 2 SATA hard drives. /dev/hda is the boot drive, but /dev/sda contains my CentOS installation, including /boot, /, /home and swap. I know for a fact that there is no MBR on /dev/sda because the system refuses to boot from it. I would like to rearrange the boot order to use /dev/sda as the boot device (mainly because I'm probably going to get either another disk drive or both another disk drive and a m/b soon that does not have two IDE connectors (I have two IDE DVD burners) and I'd rather not replace any more than absolutely necessary to accomplish this.

So, what is the best way to put a correct MBR that will boot from /dev/sda on /dev/sda if /dev/sda is the first boot device?

Thanks.

mhr