Partition Magic Fails with Error 4

I was attempting to use Partition Magic to merge my C: and D: partitions.

 

The merge starts (in boot mode), gets to "Checking current integrity 18%" then fails with:

 

Error 4, Bad argument/parameter .

 

After a restart, C: and D: are apparently unchanged.

 

Any ideas?

 

(If not, can someone tell me how to get a refund?)