My netbook came with a Win 7 "starter edition" OS, and I wanted a way to automatically backup the complete registry with each startup, as I currently do with XP, using ERUNT. (ERUNT saved my bacon on at least one occasion):
http://en.community.dell.com/support-forums/virus-spyware/f/3522/p/19298624/19567247.aspx#19567247

I found the instructions here:
http://www.winhelponline.com/blog/backup-windows-vista-registry-daily-using-erunt/

Although the instructions were written for Vista, I can confirm (after having been assured of this by the author, Ramesh Srinivasan) that this method works for Win 7 also. You can also limit the number of backups to whatever number you wish.

Note that to restore a registry backup, you have to temporarily disable UAC, and run the backup (ERDNT) with admin priveleges (in both Vista & Win 7). Same thing to manually create a backup.

You can get ERUNT here:
http://www.larshederer.homepage.t-online.de/erunt/