Lot of changes to my network recently. The old PIII-800MHz became a pfSense router for a friend, and the server is the Intel Core2 4400 at 2GHz, so quite a step up. But getting it all configured was major pain.
After putting the new motherboard into the case, the system sort-of booted, but not really. Couldn't find the kernel. As this was the server, my network was down, so not easy to download a bootable cd, which I should have prepared actually. Somehow I had a FreeBSD 8.0 disk, so was able to boot with that in the end and poke around. It appears the kernel was ad4, instead of ad0 ??? Still don't understand it. The disk was ATA, but I also put in a SATA disk which became ad6. And the MBR was corrupt or perhaps the next boot loader was corrupt. Had to reinstall to boot and set it up to load the kernel from ad4.
Putting the old motherboard in another case went wrong too as the PSU (Zalman ZM460B-APS) died in the process.