Booting from a external HD

I am running Raid O with two WD 74g Raptors.
I have a spare WD 80g WD eide drive.
Could I put my spare drive in a external usb enclosure & make a copy of the OS & then boot from it on my computer?
What I am trying to do is go from raid O to raid 1 which will cause me to loose everything.
If I could make a back up with the external drive I could then just mirror that to the the new raid aray.
Is it possible?
I am running a ASUS A8V Deluxe MB.

The easiest would be to use Windows backup to backup all of the data and make a recovery diskette. As long as the recovery diskette has the raid drivers installed it should work.

Thanks for replying.
But I am a 61yr old newb.
I dont understand what you mean.

I am sorry but I am still confused.