Backing up a webserver over an internet connection

I have a Windows-based webserver that is in the DMZ. Currently it is being backed-up (using Windows Backup) to a second partition on the drive (it is an IDE-based server, and only has one HDD, no RAID). I would like to be able to setup a more elegant backup solution, but due to cost restraints I cannot purchase any hardware or software at the current time.

I am thinking that I could implement a script to log into the VPN, and use FTPput to transfer the backup file to the backup server (once per week, since not much changes on the webserver). Any suggestions or advice on how to make this work would be greatly appreciated.