switching from amd to p3

[Doug Sutherland]

If you're getting disk boot failure then probably something 
is not right with the physical connection, the IDE cable or
possibly the BIOS needs to be tweaked to recognize the
hard drive. If there is more than one drive in the system 
make sure the one you are moving in is on the first IDE 
port so it's drive A, also make sure there are no conflicts
if you have two drives in there ie make sure one is set as
master by jumper and the other is set as slave. 

I think you can get disk boot error even if there is no disk
at all, so start by checking the physical connections and 
jumpering of drives.

The other thing that sometimes happens when moving 
drives around is that what was drive a becomes drive 
c for example, in that case you will get a kernel panic 
with message stating no root file system found. If this 
happens, then the other procedure I mentioned will 
work, booting from cdrom or floppy, loading the 
kernel from removable storage with the boot param
root= pointing to the proper location of root file system
(follow that with noinitrd ro) and then once booted you
can rebuild the kernel and update the bootloader.

What you are doing is definitely possible, I have done
it many times, building an entire system on on PC then
then moving the drive to a mobile system.

  -- Doug