Per the instructions that came with our Transformer's...
"In the unlikely event that your tablet becomes unresponsive, try a forced reboot -- press and hold both the power/lock and the UP volume key for three seconds"
To "reset" your tablet:
"Warning: These procedures delete all of your settings and data on the tablet. This includes pictures, videos, documents and other files that you have not backed up online or on a PC.
If you want to remove all of your personal data from the tablet, touch Apps > Settings > Privacy > Factory data reset.
If you forgot your unlock code, you can reset the tablet:
1. Turn on your tablet and when the Asus logo appears, press and hold the volume DOWN key. Keep holding the volume DOWN key until Android recovery text appears in the top left corner.
2. Press the volume UP key to put device in Android recovery mode.
3. When the Android recovery screen appears, press and hold Power/Lock. While holding Power/Lock, press and release the volume UP key.
4. Your tablet should show a wipe data/factory reset option. Press Power/Lock to select the reset option. "
Just in case you don't have your handy-dandy instructions that came with your Transformer.