44.5 hours later...

That's how long it took to "migrate" from a 300GB RAID 1 array to a 600GB RAID 5 array... not counting the time (probably just as long) that it took to XCOPY the data over to the RAID 1 array in the first place. The nice part is that I was fully able to use the drive and the machine during the process. Now everything is finished and working beautifully!