What happened over the weekend

[Eireann]

Yesterday, when I turned on my computer, the monitor was black. I messed around a little bit; still nothing. I bought a new graphics card and installed it. Nothing.

Today, I got a monitor from the thrift store. Brought it home, plugged it in, and yep, that was the problem. The monitor. Not the graphics card. However, I'd already bought a new one, so I went ahead and ran the installation CD on the new one. I had to restart the computer to complete the installation.

Now. The screen looks fine. But the computer insists that no audio devices are plugged in. This is untrue; my headphones are plugged in. The computer thinks otherwise.

The graphics card is a GeForce 210 1GB DDR3. Is it causing this problem? Either way, what can I do about it?

[Der Cute]

Unplug headphones. Reboot. Plug headphones in (I hope they're usb). See if anything is "seen".
You say the puter insists on no audio plugged in. Are you going to Device Manager? (sometimes you can see A thing plugged in but not in use/usable as of yet) the yellow Caution sign there.
Get there:
Control Panel
Device Manager
You'll see a tree
Expand the line at sound/vid/game controllers
Is there a caution sign?
If so, try installing drivers.
The puter KNOWS there's an audio thing but is not able to identify or use it yet
Update drivers.

The problem here is the audio at the moment. It used to work just before the new card. Ok, so we know the audio port works and so do the headphones. Let's focus on the "use" of the headphones.

PS sometimes I think your puter is possessed. it doesn't like being changed.

[lordlundar]

What's the monitor model? There could be a separate audio port(s) that needs to be plugged into the sound jacks on the computer first.

[Eireann]

Sound!

I poked around online and found that many many many others have had this problem. When I turned on the computer this morning, I hit F10 to get into the Setup screen and looked for "onboard audio". I didn't find it, but after a little searching in the "advanced" menu, I found the integrated audio, which had been disabled. I enabled it. Success!