I have a 160GB HDD at present with my OS etc on. I want to set up a RAID 0 on two 80GB HDD's I've bought then image the 160 onto the two 80's. Leaving the 160GB as a single third drive with data on and using the two 80's as my OS drive.
sure its possible, but probably more trouble than its worth.
Id keep your OS on the 160 and install the two 80s in RAID0 like you want. this is by far the simplest solution.
Ive heard many people having problems trying to get a bootable raid array. If somebody has found a failsafe way - hopefully they can share it with you.