A better response to your question can be given with a little more info.
How many GBs of data do you want to backup?
Generally, an external drive would be the choice for a large amount of data backup..or another internal drive if your computer can handle it.
Three common types of backup: cloning, compressed imaging of entire drive or selective backup.
You can choose to backup automatically or manually.
Many programs, some free, to use to backup. Windows 7 comes with very good backup software.
I use Disk Wizard to image my dual booting hdd. It's fast and easy. DiscWizard | Seagate diskwizard - How to Install How to restore individual files and folders from a diskwizard backup