Hi,
You say you have 2 new boxes, are these in addition to 1 you had previously, if you have received new boxes to replace any old ones or have received a 360 software upgrade to any box you will have lost all recordings.
As japitts said if you have received a 360 main box and mini box, (mini Box is half the height of the main box), you can only record on the main box, set both boxes to fast start or active start so the mini can wake up the main box.
Don't forget your internet connection to both boxes.
Edited to add you can check your hard drive on the main box by pausing some live TV and then carry on watching without any problems.