1) somewhere I wired something incorrectly
2) my PSU is not powerful enough. It is a 650 watt, and you can check to see if it is good enough for the specs above
3) I somehow damaged my video card while physically installing it on my motherboard.
If you all have any ideas please share them! I'm really really worried that I did something very bad here ...
1) is certainly possible. Never hurts to check.
2) 650W is enough to run
anything , even the most ludicrous two-card combos and latest processors, even under full stress, so simply booting up a normal system cannot be too much for your PSU.
3) Maybe you didn't damage it, maybe you just didn't push it deep and hard enough
Srsly, this has happened to me several times when changing the graphics card, I think that the card is in the slot but it isn't, and some further pushing (or removing it and pushing again) WITH THE POWER OFF has solved the situation. I would say this is the most likely reason.
Also, driver conflicts only come into play after BIOS has loaded, so you should still see some text on screen even if the Winddows loading crashes later on.