We get window tables all the time. We go down on embarkation day and ask to see where our table is (from the Maitre'd) .. If it isn't a window table ask him (or her) nicely if you can be moved to one. If you go early on embarkation day you have a good shot at it. But since there are many people asking the same thing they go fast. Also realize that as CF said above, the window table are larger tables and you will end up sitting with at least one other group. Maybe even 3 other couples.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013