After following the steps in my XBMC Live Drives Mounted as Odd IDs article, wherein the user modifies the label of the drive and sets it to be recognized as part of the fstab process, I found myself occasionally seeing the message that indicates that Ubuntu can't find the drive. I found it frustrating that I would occasionally reboot my XBMC setup and the Seagate USB harddrives would have issues until I power cycled them.
With a bit of quick research, I found that there is an option as part of the fstab setup called nobootwait which lets the operating system continue to boot up even if the drive isn't present. In order to add this option, take the following steps.
Open the fstab file in your favorite editor:
sudo nano /etc/fstab
Modify the line for your hard drive to add the nobootwait parameter:
UUID=1234-5678 /media/SeagateHDD ntfs-3g defaults,umask=002,gid=users,nobootwait 0 0
That's all it should take. Next time you reboot, the system should skip past the waiting screen ("S to Skip").