Blank Screen after turning off Switchable Graphics

I've been having lots of problems with my Precision M4800. After getting it back from Dell's support it worked for a while then crashed and refused to boot. Since then I've been trying to get the graphics card running again. I decided to try turning switchable graphics off and on but now my screen is blank.

When I say blank I mean the display backlogged doesn't even turn on. When I power it on, the indicator LEDS light up normally and I can hear the computer working but nothing shows up on the display. I've tried mashing f1, f2, f6, f8, ctrl+alt+enter, delete, Fn+F1, Fn+Esc and f12 during startup but still nothing shows up on the display. I've also tried removing the battery and holding the power button for 30 seconds. I ran the LCD built in self test and it passed, so the problem 100% isn't with the panel.

If it helps I also ran Preboot System Assesment twice and while nothing showed up on the display, the computer beeped the code 333 both times. This indicates that "PSA diagnostics did not record the system user pressing Y or N after the video test. Please ensure that you accurately answer questions that are prompted during the diagnostic." Unfortunately, nothing shows up on my screen so I dont know whether to press Y or N. I gave it a go anyways pressing N whenever it beeped at me (the beeps before the error code) but it just stopped beeping after a few times.

I don't have any personal data so its fine if I have to do some sort of complete reset, I just need it working ASAP. Please help, thank you.