The Serial Number is prompting for the CD Key (same thing when installing, different once installed).
Found on the CD jacket when purchase of the CD has been made, or received via email when a Download purchase has been made.
It is a 6-6-12 combination of numerics and characters, generally starting with D32...
Make sure the dashes are present and any 0's are in fact zeros, not the letter O.
If still having a problem, please contact us:
Datawatch Tech Support