SONY XPERIA ST21I2 ADB DRIVER - Sony Xperia tipo dual ST21i2 Smartphone - Unlocked | Current

Install The flashtools drivers:Flashtool drivers exe Google Drive
After install plug phone in to PC(make sure USB Debugging is enabled on the phone) if driver does not install itself go to Control Panel --> System --> Device Manager and look under Other devices there will be one named Sony Xperia(will have a yellow Question mark next to it) right click choose "update driver". Choose "browse my computer for drivers" on next screen choose "Let me pick" option. under manufacturer choose Sony Ericsson and then install the ADB driver(If the Sony driver does not work try installing the google ADB driver that can be found in the Android SDK)