possible options/ideas in no order:
Free Image maker tools are available commercially, some are free for personal use:
1. windows has built in imaging software, see backup applet.
Other exampleMacrium reflect free: http://www.macrium.com/reflectfree.aspx
2. linux solutions free and nonfree
I'm thinking you could schedule backup imaging when computer not in use
local or cloud backup
Option B: , RAID striping, or mirroring... you would have to research
Edit: setting up a cheap software raid array is possible in Win7pro. Reference: How-to-Geek
set up an automated server (cheap computer) to do this when not in use.
Option C: cloud backup... a paid/free solution such as carbonite, or other 3rd party
Option D: backup changed data to blue-ray