I can't unlock my Nexus 7 - ASUS Google Nexus 7 Tablet

Dear Helen,
Password/Pattern/Facelock passwords can be 'Bypassed' by several ways, which are mentioned in the link below:

Android Guide Hacking And Bypassing Android Password Pattern Face PI

I haven't tested those methods, so be careful. And there are a few note to pay attention to:
- I'm not the provider of all those methods. I'm just copy & pasting the link so that you can refer, so all the credit goes to the author of the article.
- I'm not responsible for any damages caused by one of the methods, so do it at your own risk.
- If you haven't heard of 'Rooting', it's best not to know as it could void warranty.

Regards.

You can try resetting the password or pin through the Android Device Manager page.
I have done this 5 or 6 times for myself and clients without erasing everything with a factory reset.
It is worth a try before wiping out your device.
Since Google's help page didn't have this I wrote it up here.

http://www.whitesplowing.com/nexusunlock.html

There is a good chance to do a hard reset but it wipes out all ur settings..for better info go to this link
http://youtu.be/Txn2v6xPcXw
let me know if it works for you.
Chad man