I have just installed fedora 14 on a seperate hard drive and want to use fedora 12 grub bootloader to it.

When I connect the fedora 14 hard drive to the system and try to boot fedora 12 via grub I get a "Kernel panic not syncing attempted to kill init message"

The kernels both boot okay when hard disks connected separately

my system hardware is gigabyte ga-x58a-ud mother board and all western digital sata hard disks

Any ideas

The problem is that your are changing the available disks.

What you should do is leave both connected at once, and then correctly configure grub to boot one or the other.

The reason is because grub is told which hard disk to look at for the root partition of the system being booted. If it's told to look at the first hard disk and Fedora 12 is the only connected disk, then it will work fine. But if you have both connected and the first disk is 14, the second disk is 12, grub will still do as it was told and go to the first hard disk and try to boot from it; which fails. The same goes the other way round.

You need to connect both disks at once and then tell grub that one is on the first hard disk and one is on the second.