what is system image exactly? and do you have a recommend software?
Recommended software would be Macrium Reflect Free Edition. There's a tutorial on it on this web site.
http://www.sevenforums.com/tutorials/73828-imaging-free-macrium.html?ltr=I
It makes a "system image" file that you can later "restore" to a hard drive, also using Macrium.
You can think of a system image as an exact replica of one or more partitions on your hard drive---typically the C partition. You choose which partitions. The system image file includes EVERYTHING on that partition--Windows, licensing information, installed programs, pictures of your cat, and whatever else is on it. The system image file isn't of much use UNTIL it is formally restored, which is done by booting from a rescue disk made from within Macrium. If the rescue disk won't boot, you can't restore and are dead in the water. When that one file is successfully restored, you will then have a fully bootable hard drive in the same state as of the time you made the system image--yesterday, last week, last month, or whenever you made it.
Success rate high, but not infallible. You need to know what you will do if it fails.