or it will just wipe up the new Windows 7 build with the previous one i have backed up
If you created a "full" disk image and do a restore, Acronis will totally replace what's on "C" with that image. It is not like a Windows "in place reinstall" where, using your Windows CD/DVD you can reinstall the OS and leave the data and applications (and related registry entries) alone.
Be careful with new versions of Acronis (I "was" a long time user). Since version 8 or so it has become very buggy. Look at the Acronis forum sometime and see the pain. There are alternatives, but an image is still an image and that means going back in time.
If I'm wrong, someone will correct me.