Your welcome! We should take this discussion offline (PM) or create a new thread in an appropriate section if you need any further assistance other than these quick links I am providing below:
The below links should get you started. Just be extremely careful when partitioning, one wrong move and you could inadvertently reformat (wipe) an entire disk. I would restrict any initial partitioning effort to just your external backup-disk being careful to preserve the existing file backup partition (partitioning the free space to add another partition assuming external disk is large enough to partition effectively). Or... don't risk anything and just buy another external disk to use 100% for image backups. Backup hard drives are cheap now-a-days and they are good insurance that you will never have to pay a ransom or hire a recovery expert WHEN USED PROPERLY.
http://www.wikihow.com/Partition-Your-Hard-Drive-in-Windows-7
Not sure which version W7 you have, it may or may not have system image backup utility already available:
https://technet.microsoft.com/en-us/magazine/ee872304.aspx
If you don't already have the system image utility in your version of Windows 7 Acronis True Image is very good:
http://www.acronis.com/en-us/personal/computer-backup/
Hope this helps.