I'm trying to load linux onto an old machine - then the motherboard died. I've got a new motherboard ASRock K7NF2-RAID. Linux now keeps telling me

Kernel panic - not syncing : VFS : Unable to mount rootfs on unknown-block(xx,xx)

Each distro gives me a different numbers where the xx are. I've run memtest and that comes back with a pass each time.

Processor is XP2500+, 2 PATA HDD, one CD-RW, one DVD-ROM, 256Mb RAM, nVidia GeForce2 graphics.