|Look at the link below to understand what a dynamic disk is. |
You MAY be able to rebuild the dynamic volume using test disk.
If you don't really want to do that then you MAY be able to recover the data on that hard drive using a live version of Linux or professional recovery programs. How much data is on the second hard drive?
You can get testdisk at the second link below. Be sure to read all the instructions before using.
If you connect the hard drives just like they were connected on the old motherboard the dynamic volume may show correctly again. Not sure about that but worth a try. If both drives were on one cable then connect the same way.