<<Why can't make a Backup!>>
First...don't worry about your English...most citizens of the U.S. don't have a clue about a second language and we don't do very well with English either, If you have any doubts, just take a stroll on the Internet
Exactly what steps are you taking to attempt backing up Win 7? What software are you using?
I find that the best free software for making a system or hard drive backup is Macrium Reflect FREE Edition - Information and download - http://www.macrium.com/reflectfree.aspx
What errors are you getting...and when does the error occur?