<<<Is there an easy way to remove the second partition without destroying the data on the first?>>>
There is no problem in deleting the second partition and doing so won't affect the main "C" drive partition. However, it will create Unallocated Space on the hard disk, the first partition won't automatically expand to take in the additional space available. You would need a program such as "Partition Magic" to modify the partition structure without loss of data in the first partition.
<<<I am backed up to an external HD so any mishaps can be repaired>>>
If your backup is with a program such as Acronis True Image, you could delete the two existing partitions, create a single new partition and then restore the Acronis backup of your "C" drive into the single partition.