The drives' serial numbers are stored in flash memory - in what is called the "magic number" - you need to find a way to edit that.
Actually - if the drives were"not updating their directories" that would suggest that you already have some level of data corruption, and if that is the case, a reformat would not be such a bad idea. 800 megs of data is not that much.
If you're using anything other than RAID0 or JBOD you should be able to get access to the data by installing one of the drives (for RAID1) or both of them, one at a time (for standard volumes) in a computer running either linux or Windows XP and the ext2ifs drivers.