Why won't my new video card work?

Does the motherboard have video?

If so, does it boot using that onboard video?

If so, there may be a BIOS setting to tell the machine which video port to use first.

What @jaytkay said would be my first guess too. Besides: maybe you really didn’t press it into the PCIe slot properly? That’s usually my biggest problem. I hate forcing hardware, but sometimes you just have to.

Can you post more information about the machine? Besides a BIOS setting, maybe the BIOS just needs to be upgraded. Never used Radeon, but I’ve had that problem with older nVidia cards.

The system won’t boot using the onboard video either.

I have pressed the card in as hard as I dare without breaking it. It still won’t work.

I’m not too sure about the system specs. My brother built the system, but he’s working a little too far away now.

This also isn’t the first video card I’ve installed. I installed one on my own computer and one on the living room computer… They both worked fine, but this one doesn’t.

Try installing the card into a different computer. If the card does not work on another known-good computer, then you can consider the card bad and RMA it. If it does work on the other computer but not the first one, then there might be some incompatibility in BIOS (are you using UEFI?) or possibly a bad slot (maybe you can test with another card?)

Sounds like 1 of two possibilities. Either the card is bad or you are not powering it properly. Some video cards require a separate power connection (usually a 4 pin plug)

Does it boot with the on board video without the other card plugged in? If not, you may want to make sure you didn’t knock out one of the RAM DIMMs when you were plugging in the Radeon. Some motherboards can be a little tight with component placing.

@ARE_you_kidding_me reminded me of another possible problem: maybe the power supply isn’t providing enough power?

A Radeon 5450 is a low-power card without a separate power connector.

Very unlikely it’s a power problem, unless the PC is a small one with a very, very small power supply.

The computer does boot with the onboard video without the new card installed, and the power supply is 550W, and the system is only running the basics (One hard drive, one optical drive, lan only (no wifi card),etc).

And it doesn’t work in my other computer, either.

Sounds like a bad card, then. You’d better RMA it if you can. Unfortunately there isn’t much you can do to test the card further, although you might want to have a look at the capacitors on the board to see if they are swollen or leaking.
Or you might not. At this point it doesn’t matter, since the card fails on two known-good machines.

It’s dead, Jim.

@mrentropy I believe it is one of the extras wearing a red uniform.