Dick,
Two ways to go on this... You can use Super Duper (which just updated to SL support), or plain old disk utility. I had made an image of my 10.5.8 system, erased and partitioned the external USB drive, then used disk utility to restore the original 10.5.8 system to that drive.
I booted my MBP with the DVD (and Option key) from a cold start, selected the Install disk to boot from and installed SL to the external drive. It is working perfectly (meaning the external drive) for testing. Still allows me access to my other externally connected FW and even SATA drives (reinstalled the SI3132 driver). When I think I've read enough and tested my own stuff enough, I'll update the onboard hard drive.
Even running from an external USB, there is a very noticeable performance difference (for the good) running Snow Leopard. Now if they can fix some of these issues, get an SIL3132 SATA driver that is certified, etc..
Jay S.
Message was edited by: Jay_S