Just in case it might help, if you backup an image using Windows Backup and Restore, it seems to need a drive as large or larger as the total partitioned space backed up to be able to restore the image.
So, can you reduce the size of the Win 7 partition enough to allow the backup to a 64 GB drive? All other space on the 2 TB drive probably needs to be left unallocated before you do the backup image. If this is a RAID, there may be a possibility the second partition would also have to be unallocated, but I have no experience with RAID.
If not that, maybe another utility, like TorrentG suggested or a pay version of Acronis.
Have you been having any problems using a 4 TB partition? I heard 2 TB was the limit, but that may just be for the OS.