NTBackup creating non-backup folders?

This question refers to the NTBackup.exe utility on Windows Server 2003. Our server at work contains 4 drives set up in a RAID 1+0 array.

A few days ago I completely re-made the entire schedule of backups on our server at work using Windows Server's built-in NTBackup.exe utility backing up our server to an external USB HDD. It is set to create an incremental backup of our 3 main data folders on the server each week night (Data, Archives, and Downloads), and then a full system backup each weekend. On the external backup hard drive, it creates those as .BKF backup files.

So now the weird thing is that it also is creating a copy of the Data folder on the backup hard drive, not as a backup BKF file, but just a straight copy of the folder and its contents. What's even more weird is the actual Data folder on the server contains around 60 GB of data, but the copy on the HDD is only around 40 GB. The incremental backup files from each week night are around 4 GB (about right for the amount of files that are changed or worked in each day).

So what would be causing the Data folder to get copied to the external HDD's root directory, and why would it only be that folder? I tried deleting that folder off the external drive one day, but the next day it was on there again. I believe it is over-writing that folder each night, along with creating the normal +/- 4 GB BKF incremental backup file. I can't find anywhere that specifies a copy of that specific folder to be placed on the backup HDD. Anyone know?