Swapping hard drives one mirrored-doors to another

[Jim Robertson]

I have an original "wind-tunnel" dual 1 GHz and an early 2003 (800 MHz
Firewire) dual 1.25 GHz G4. I installed all my wife's stuff on the dual
1.25 GHz machine (she's coming from a 15" flat-screen iMac), and she can't
stand the noise. This IS the 2003 model, not the "Wind Tunnel" box. I've
finally installed the fan/power supply swap kit in the latter, and it's
DEFINITELY quieter. My wife says she won't use the dual 1.25 GHz machine
because of the noise, so I'm considering taking the hard drive(s) from my
1 GHz machine and swapping them for the single drive in her 1.25 GHz
machine. I'm assuming that there aren't differences between the two
machines that would make the OS on one not boot or run on the other, and
vice versa. (Both have 10.2.8 with all updates current).

Is there any reason this shouldn't work?