you have to have exact partiton sizes, if you have, 100 gig partition and on the other disk a 120 partition it will automatically make 100 gig striped partition and leave 20 gigs, so i usually make 1 gig partitions on each drive strip those and put my swap file on that, and create a spanned volume with the rest so that 100gig and 120 would be 240 put together as one partion, another thing to is that you cant strip the partition that windows is on,