Option 1: Completely reformat your hard drive, and reinstall your OS. During the installation process, just remove all partitions and install it on the entire drive. Since you have backups, it wouldnt be a bad idea.
Option 2: Get a program like PartitionMagic, and use it to delete the partition. You may not be able to combine 2 NTFS partitions, I don't think, but at least you can use the space for whatever else you want. Maybe install Linux...
If you wanted, you could even take the Windows CD they gave you, copy the contents to your hard drive, remove the Dell crap, then burn it to a bootable CD with EasyBoot or something. Then use it to reformat your drive with only one partition and install your new, "clean" version of Windows.