Alright so I recently installed a GTX 750 Ti into my PC it requires 400 watts and runs at 60 watts.

My PC has a 300 watt PSU and I've been running a AMD 7750 which requires 400 watts too and runs at 55 watts.

I can clearly run Pcie 3.0 for the 7750 and 750 are both 3.0 so I got the mobo and psu down(maybe?) for the most part.

My PC is this right here http://www.microcenter.com/product/405189/DX4870-UB21P_Desktop_Computer

ISSUE: I boot on the computer with my HDMI cable connected to my new graphics card and I get a screen that shows the Gateway icon and it says "Press DEL Enter BIOS Setup, F12 Display Boot Menu"

I press F12 nothing happens I press DEL nothing happens and after about a minute it's goes to a blank screen that shows just this in the top left corner and it's flashing: _ 

I attach the HDMI cable to the mobo's integrated graphics card and it won't display anything until I take out the 750 card either.

I don't feel its a PSU issue, do I have to update or change something maybe?

Any help would be greatly appreciated.

EDIT: alright so it seems the last bios update was from 3/12/12 and this video card is from 2013 so maybe updating my bios would help?

Jesus I wouldn't stick any sort of graphics card in a PC with a 300watt power supply, you know that would be the things peak rating? like if it's 1 or 2 years old it's probably outputting somewhere far closer to 175-200watts now? you're really risking a major shortage and fire trying to do what you're doing there. If you are hell bent on trying to run it with that PSU definitely make sure all the USB hubs are empty of anything you can do without for the time being, even those could push that over the limit .

Running low powered cards on a low powered PSU shouldn't be an issue

Last time I remember... A video card doesn't really need a Bios update to run it, usually the only thing you need a Bios update for is to install a new CPU... Hmm, interesting however... Does your 7750 work again if you put it back in?

It's not just the card tho which takes psu wattage, every harddrive, dvd drive... usb mouse/keyboard will eat through the amount of power that 300watt thing would be outputting by now, like I said it might be rated at 300watts but that is the optimum like absolute max that any of that make of psu could produce on day 1 out of the box, average you'll get from it will be a fair deal less than 300 and then less again if it's a year or 2 old.

A bios update isn't going to make you have more power simple as that, if you want to try you can disconnect stuff you don't need like I said already tho, take out the power cables from your dvd drive and any thing basically which isn't needed for the PC to start up with the graphics card attached. go from there.

Yea, I've read that a Bios update was only for a CPU though I figured it might be feasible.

And yes the 7750 works fine.

i uninstalled the 7750's drivers before I installed the 750, Would it make any difference if I reinstalled the 7750's drivers and than took out the 7750 and put in the 750? 

Not really, what OS are you running?

Also, just to be clear, you can't get passed the Bios with a 750 right? Like it just shows the logo and then it just doesnt work?

Yea I know I understand, I feel I'm a good amount under 300 Watts and as I said I've been using the 7750 so I don't know if 5 watts would be the difference here. But I see your point and I appreciate your insight. I'm just hoping it isn't the PSU, which is very well could be.

if it would be coming down to a couple of watts disconnecting an internal dvd/cd drive would be enough to get it back into a bootable state, could the card just be dodgy? was it new or tested in another machine first?

Windows 7

And yeah with 750 I get the bios options and the gateway logo and after a minute or so a blank screen with an underscore in the top left just pulsing.