HP Proliant – Mirror not setup – need to setup now

I have an 350ML in production for several years, it has two 73 Gb drives, 2nd is empty. RAID 1 was never setup.

(1)
Should I setup RAID 1 with Windows 2003 SBS interface
or
find some HP utility to do the setup

(2)
Will creating mirror now erase or place disk 1 at risk?

Thanks