reassigning boot drive

[modelt20 at canada.com]

Hello All:

When my computer was assembled, the CDROM was attached
as master on the first (primary) IDE channel, and the
hard drive was attached as master on the second
(secondary) IDE channel. 
It has now become desirable for me to rearrange my
drives, but I have accumulated a lot of configurations
and settings on my hard disk, so reinstalling is not
attractive. 

Has anyone tried reassigning the boot disk from ad1 to
ad0? What pitfalls are there?

Thanks in advance.

Harold