I installed a system, now I have no power

I just bought a 2002 Blazer and I tried to install two 12's and an amp. After I got it installed it sounded great for 5 min. then the subs, flickered then cut off, then my amp cut off, now nothing works. When I turn the key it is silent (every once in a while I will hear a little bit of clicking). And to top it off, I cant get the key out of the ignition. Any ideas what I did?
***I wont be installing anything else myself***

My goodness! I'm not sure about the electrical problem, but about the key... is the steering wheel locked? My 98 blazer's steering wheel will lock, and I can't turn the key at all - I have to wiggle the wheel side to side while turning the key. My 86 IROC-Z and 85 Blazer do the same thing, so I assume it's a Chevy thing. I can ususally get the key out, though, just can't turn it. If the steering wheel is loose and free-turning, then I have no idea why a key would not come out of the ignition, assuming the switch is in the "Lock" position. It is pretty easy to accidentally put it in accessory (one back from lock), and they key won't come out at all.

Just a shot in the dark about the amp - could you have overloaded the stereo system (i.e. will the radio work the way it was originally set up)? Does the system work without the amp? If so, maybe the amp is faulty. I've never put in an amp, but I've put in plenty of speakers, and they flicker sound every now and then when they have loose wires - you should check all connections as well.

I can turn the key but the engine wont turn over. When I turn it back it, it wont turn all the way, it stays in lock. I unhooked everything and the car still has no power.

Oh! I misunderstood your post - though you meant the radio had no power. You mean the whole Blazer has no power... If the battery is okay, I would guess a problem with the ignition switch, a blown fuse/tripped breaker in the fuse panel, or a blown fusible link. If you have a multimeter/voltmeter, you can check at the fuse box under the hood to see if you have power there. If so, I would guess it's a problem with a tripped breaker or blown fuse, and you can use the meter to check them as well.

First off, check the battery...if thats ok, check the alternator. If you were running a big amp, that takes a lot of power, your alternator will die. If you find out thats what it is, go out and buy a power cap and hook that up to your system, it makes a big difference...about the key locking thing, I have a 97 blazer and just the past couple of weeks mine started to do that, i can eventually wiggle it free, but it takes a minute and gets really frustrating...anyways good luck with that.

Here is something simple, check the positive and negative connection at the battery. It is probably just a bad connection when you hooked up the amp wire. Make sure it is clean and tight

Do any dash lights come on? Dome light? How is your system wired? You do/did have a fuse in your main line right?