When I google the HD serial (as I said) I immediately see it's Seagate Baracuda 7200. I'd run bootable Seagate Seatools
which can sometimes repair problems, followed by Disk Check
from the installer's Command Line once you get into it.
I thought you had already tried booting the Dell DVD. See if you can boot into System Recovery Options
to run Startup Repair a few times with reboots, System Restore if it's not automated by Startup Repair, Disk check. If these will actually run then it's likely not the HD and you have all the possible fixes to try in Troubleshooting Windows 7 Failure to Start
leading up to file rescue to run Dell Windows 7 PC Restore
or get the superior Clean Reinstall - Factory OEM Windows 7
with that same Dell DVD.