No sounds from PC with audio device installed, updated and enabled.

My Lenovo G575, Win7 64, stopped outputting audio today after I plugged in a Jawbone Jambox into it by USB for the first time. A small window popped up stating, something about software or drivers being installed (I don't remember exactly). After the (install) process was complete, I unplugged the USB, and the audio from the laptop no longer worked. I immediately did a system restore to an earlier date when the audio worked. After the restore, there was still no audio coming from the internal speakers or from the output jack. If I plug in headphones into the output jack, all I hear is faint static. There is not faint static, or any sound, coming from the laptop's internal speakers, however.

Next, I:
1. Control Panel >Hardware and Sound >Manage audio devices
In this window, it shows that my Default Device (Speakers, Conexant SmartAudio HD) is enabled. This is the only playback device listed, and the meter bar displays activity if a mp3 file is played, but still no sound.
I have right clicked on the playback device in this window:
A. Enabled and disabled this playback device, and restarted my computer. No effect.
B. Configured speakers. No effect.
C. Test. No sound, but activity displayed on the meter bar.
D. Clicking Properties in this window:
General: This device is enabled
Levels: 100
Enhancements: defaults restored
Advanced: defaults restored

2. Control Panel > All Control Panel Items > Troubleshooting > Hardware and Sound > Sound > Playing Audio: "Troubleshooting couldn't identify the problem"

Please share any ideas you have on what the problem could be, or suggestions for steps to restore my audio. Thank you.

Thanks for the reply. I forgot to mention that I tried the uninstall, re-install step yesterday, to no effect at the time.

After going through all the steps listed in this thread, I shut down my PC for a few hours and let it cool off. When I turned it back on, the sound was restored.