I seem to have really borked my system, and I don't know how to unbork it. I've been having a few minor issues with some things, so I figured that it'd be a good idea to take care of a few things that I had been meaning to take care of, but just hadn't gotten around to, in hopes that they'd fix the issues I'd been having. (Machine's been a bit noisy of late.) Here's what I did, after powering down the machine and unplugging everything hooked up to it, I opened up the case, pulled out a fan that had died, replacing it with an identical model, yanked out one of the video cards and stuck in a newer card by the same manufacturer. Used a can of compressed air to blow all the dust rhinos and balls of cat hair from the machine, put it back together, and plugged everything back in. Now, I made one change in how I plugged things in. The USB hub I had plugged into the front, which has the Bluetooth dongle, printer cable, and webcam hooked up to it, I moved to the back. (I've got a bad habit of catching the cable with my foot when I get up and have already destroyed one of the USB ports on the front.) I boot the machine up, everything goes fine. A couple of minutes after I log-in it says that it needs to reboot to update the video driver software (not really a surprise). I do the reboot, and that's when the problems start happening. For some reason, it won't see the Bluetooth keyboard. I grab an old style PS/2 keyboard, plug that in, it doesn't recognize. When I hook up a USB keyboard, it sees that just fine. (It also sees my Bluetooth trackball just fine, as well.) I log in, let it finish going through the last bits of the start up/set up procedure, and then try to get the Bluetooth keyboard working. Nothing. Yank the batteries out, replace them with fresh ones, still nothing. I also notice that Chrome won't launch. Other browsers on my machine work just fine. I say "the hell with it" and do a system restore from a 2 week old back up. Bluetooth keyboard works just fine, but Chrome still crashes. I do a redownload and reinstall of Chrome, that fixes that. Next I check out the audio side of things. The mic works fine, but when I go to playback the file I recorded in Audacity, I can't hear anything. I check YouTube, nothing. System audio, however, plays just fine, as does anything I select in iTunes. I've fiddled with the obvious settings for the audio output, and I've managed to get garbled audio when I play a video on YouTube or from Audacity, but nothing. From Skype, I get intelligible audio, but it's so low you can barely hear it. How do I fix this?