If any of your dynamic drives has become read-only you can use diskpart to clear the readonly flag. Check the MS support article on the utility A Description of the Diskpart Command-Line Utility
In sort, you launch diskpart from the command line, do a "list volume", then "select volume X" where X is the read-only volume and finally "attribute volume clear readonly".
Note that the volume has probably become read-only for a reason and this won't fix the problem. And you can not clear the readonly flag on XP unfortunately.