In order to hard reset a Sony Ericsson T290, you should perform the following steps.

Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Sony Ericsson T290 device will be brought back to the default configuration of a brand new device.

1. Turn on the phone.

2. Select Menu, then Settings and Backup & Reset.
3. Confirm. 
4. Your phone will now reset and restart, completing the hard reset.