Been working on this issue for a couple days now. I meet the EVGA box requirements for the gtx 750ti graphics card:
 
400+w power supply with 20a on 12v rail (I have the Corsair CX500, 38a on the 12v rail)
Windows 7 64bit OS
PCI-E x16 2.0 Port on motherboard.
 
My computer is the HP p6520f, with the corsair CX500 psu, and the EVGA gtx 750ti. I have 2 monitors, the Wacom 21ux Tablet monitor and the 32inch VIZIO VAM320M.
 
Current nvidia driver 344.75 installed. Nvidia Control panel recognizes both monitors (Wacom Cintiq 21ux, 32inch VIZIO VAM320M) when plugged into DVI and HDMI ports, but does not send to my VIZIO 32inch. I have swapped between 4 monitors (an additional ASUS 21inch and a 22 inch Samsung TV), checking cables and every monitor works on DVI port (even with DVI-VGA adapter). The combination of 2 smaller monitors work (excluding VIZIO 32inch TV), but the combination of DVI port to 21ux Wacom and HDMI to 32inch VIZIO does not work. My 32inch VIZIO works with HDMI-to-HDMI (and HDMI-VGA adapter to VGA TV port) as a standalone monitor for this gtx 750ti. My CX500 power supply is sending the right amps to the card, it maxes at 38a on the 12v rail. My BIOS settings are set to the PCI Express slot, not the onboard graphics.
 
Running out of ideas. My previous card was the Galaxy Geforce 210, a cheap 4 year old card that has 1GB of ram that was pushing to BOTH of these same monitors with no additional power, running a Thermatake TR2 430w RX with only 14a on the 12v rail! No requirement on the box for amps on the 12v rail.
 
What's also interesting is that when print screening this image (before cropping), I was able to capture the extended display!