Hi. The hard reset procedure for the device model are is as follows
Press and hold the Volume Up "+" button and the Power button at the same time
Tablet power on (you can then release the keys at the Toshiba Logo) and displays 3 Icons. Using the volume key, select the middle Icon of the box with the arrow coming out of it. Perfom the select using the power as you would with the "enter" key (remember this for the entire process)
On the next screen, Scroll down to and select the "Wipe data/factory reset) - then scroll and select "Yes - delete all user data" (performing your selections with the power button). DoOPLEASE NOTE, THIS WILL WIPE OUT ALL SETTINGS AND INFORMATION YOU HAD ON THE TABLET.
Once that is done, select (with the Power button" Reboot now' and you will be brought to the initial set up screen.
Well done, you have reset your Toshiba AT7-B8 (Thrive to factory defaults/settings).