back up for a factory reset

You can perform a factory reset by going to menu>privacy>factory reset. This will reset your phone to the state it was in when you took it out of the box, except you will be on system version .215. All downloaded apps, contacts etc will be deleted. There is an option to not wipe your external sdcard. Choose this option. You can backup all contacts, music etc to your external sdcard and they will not be wiped when you do the factory reset. If you have a gmail account and have selected to have your contacts and calendar sync'd with gmail then as soon as you re-establish your gmail account after factory reset gmail will automatically replace/sync your contacts and calendar back to your phone. It will also automatically download the apps that you installed from the Play Store if you have previously selected gmail backup and sync.

You can also download an app like Astro File Manager (and there are others) to backup your apps, data, contacts, pic etc to your external sdcard. External sdcard is the operative word here if you haven't guessed. If you are rooted then you can use something like Titanium Backup to do the same thing. Doing a factory reset will break root so you will have to re-root after you've done the factory reset.