The best bet for storage is to run the 2 drives in non RAID or JBOD mode but that does not seem to be an option as far as I can tell. If you really need that much space for storage then you do NOT want to use RAID 0. You CAN but it is a bad idea. If there is any error or 1 drive fails you lose EVERYTHING......no way to recover it.
If you understand all this and still want the RAID 0 for storage then this page should help you.http://www.imaging-resource.com/ARTS/WDSTUDIOII/STUDIOII.HTM
I think you just insert the CD that came with it then launch the WD RAID manager software then you should be able to change it.