You need to clear the settings.
this can be done a number of ways, but for laptops typically you remove the cmos battery.
Unplug the laptop from the wall.
Remove the laptop battery.
Disassemble the laptop taking careful note of screw location and order.
disassemble until you see the silver button battery. This small watch battery is what holds the BIOS settings while the PC is off - removing this power source causes all settings to be lost.
Remove the CMOS battery for at least 5 minutes to allow all residual charge to leave the laptop, and cause your bios settings to be lost (no data will be lost).
Reinstall the CMOS battery, pin the laptop back up, and you should have your integrated graphics back on. (along with all other BIOS settings being back to factory)