OP.
The video card should show the POST screen (the stuff you see before windows starts loading. BIOS, boot menu, computer logo...etc). The drivers don't matter at this point. Nothing in windows matters at this point, you may unplug your hard drive all together.
If your motherboard has an internal video card, then that means it will somehow need to decide which video device to use. The internal one, or the one you installed. It can do this automatically, or sometimes you need to tell it what to use.
You should unplug your hard drive to prevent booting into windows every time. Then remove all video cards, and try to just get the internal card hooked up and working. After you have it working, you should go into your BIOS and try to find video card options that will let you switch to an external card. Change that option, shut down the computer, insert your new card, plug it in, and turn it back on.
If that doesn't work, and you configured BIOS properly to use that card, then it means that either the card is damaged, your installed it incorrectly, or its simply not compatible.
EDIT: To those talking about a fan not working. Fans are an extremely poor indication of anything. Some fans draw their power from a incompatible bus, others wont. Some draw the power from the fan from the power supply via the additional plug the card has, others don't. Fans mean very little and can't be reliably used to diagnose anything.
Also, I had a 200W power supply that ran a video card that demanded something like 350W. Everything turned on and worked. None of this is reliable information.
EDIT2: I'm also a pc repair tech who owns a repair business.