New I/O mobo

[Ben]

Dear members,

I'll bash in right away.

Here is what happend:
1) I replaced my old motherboard with a new one, and reconnected all components, that where on the old board, to the new one.
2) Booting did go well, till the message: "Root mount failed".
3) I redifined the mount points of / /tmp /var /usr via Index>label and toggled N to Y (Boot-cd), just like it was on installation.
4) Booting didn't go well, so I let the boot-cd create a new MBR.
5) System started up fine, but all users are gone, no root-password needs to be given when loggin in, mount directories of previous harddisks are gone. Bottom line, I don't recognize my old system's directory structure, it's like a new system. (No, I din't format, re-sliced, etc).

Questions:
a) What to do to get a system up and running after putting a harddisk on another (S)ATA channel on the motherboard? (So, I don't screw up next time).
b) How could I get my old system back, or this not possible because I screwed up?

My system:
Old board ABIT BX-133, new Abit VA6
FreeBSD 5.3 RC1.
Already installed, so no new installation.
Disk with OS: MAXTOR 40GB.

I searched freebsd.org, google.com and several forums. No relevant information could be retrieved by me.

Thank you very much for your time.

Kind regards,
Ben