Sound Troubles

I recently turned on my laptop (Lenovo T410 running Windows 7) only to discover that there is absolutely no sound. It first told me that "no audio output device is installed." I turned to the web for troubleshooting advice. I have tried upgrading and downgrading my sound drivers, to no avail. It now tells me that "No speakers or headphones are plugged in," and it won't even respond to my actually plugging in a pair of headphones. I have even attempted to disable devices and reenable them, but the computer won't even allow me to do that. This is immensely frustrating as I listen to music almost constantly while I'm working. Any advice would be appreciated.

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