Win XP installed on 2 HDD's?

I am pretty sure this would work, but want to ask, just in case.

I have a new HDD (we'll call B) and want to do a clean install of Win XP on it. I currently have XP installed on a different one (A) (both are SATA)

I want to keep the installation on the current drive, just in case there are problems - will that work okay? Could I go back and boot from A if I wanted to at a later point?

Thanks,

Aza

some motherboards won't allow which HDD in the boot order, there is only hdd and BIOS looks at all the HDD's for the active partition, personally, I 'd remove the old HDD and do the install fresh on the new Hdd then get a extenal box for the old drive and use it that way