Sorry Boogs,i sort of beat you to it.

A couple of days ago I split my 80gig into two 40 gig partitions using Partition Magic.
I kept my original XP installation (without SP1) on one partition,and installed my XP SP1 slipstreamed on the other.
The reason i went for a dual boot was so that i could see how stable the SP1 version is.

BTW,i also edited the boot.ini so that the older version is the first one on the boot option.

Works like a charm.