Hi Lyndhurst,
I have a Windows Vista Home Premium as well on an HP Pavilion desktop. The information I compiled here came from the Windows Help and Support, hopefully it is available on your computer as well so that you can click the troubleshooting links on your PC as I doubt the copied links will be effective. Again, I hope it will help.
Troubleshoot problems with line-in/microphone
The following provides solutions to a variety of problems that can occur when using microphones and other line-in sources (such as tape players, record players, and other types of sound devices).
Make sure that Windows can produce sounds from the speakers before using this article. If the computer can not play sound from the speakers, please refer to There is no sound or low sound on my computer.
Use the following steps, in order, to test for an audio signal, check hardware and connections, update audio drivers, and configure Windows sound settings.
Step 1: Test for an audio signal
Use this process to find out if Windows can detect an audio signal from the microphone or from the line-in port.
Note
If you are testing the line-in port, and if the source device has a volume control, keep in mind that turning the volume up too high on the source device can cause distortion and may damage the audio hardware. Start with the volume low and slowly turn it up until recording is at the desired level. Never turn the volume up more than half on the source device.
1. Click to open the Sound Recording window.
(The following snippet is what the Sound Recording Window looks like.)
2. To test the microphone, speak into it. To test line-in, send a signal to the line-in port from the source audio device (press play from the audio player). Look at the gray bars next to the line-in device name on the recording tab:
If the gray bars next to the device name change to green, this device is active and an audio signal is being passed through the microphone or line-in port. This step shows that problem is related to sound settings in the software that uses the microphone. If you have not already done so, set the selected device to default and adjust the levels as shown in Step 4: Configure Windows recording settings. Once the device is set to default and the levels are set, use and adjust the sound recording or voice carrying software.
If the gray bars remain gray and inactive, the device is not recognizing a signal. Leave the recording tab open and go to the next step.
Step 2: Check connections and hardware
If possible, connect the microphone (or the source device used for line-in) into another computer or audio device. For example, to check a microphone you can plug the microphone into a tape recorder. If the tape recorder can record sound, the microphone and cable are good.
If a microphone or source device does not work with another audio device, replace it.
Once you have verified that the microphone (or source device) is good, plug it into the correct jack on the computer. Consider the following while checking the connections:
The microphone connector is usually pink.
The line-in connector is usually blue.
Disconnect and reconnect the plug. Even if the plug was already in the correct connector, reconnecting may help if there is a connection problem between the plug and socket.
If you are using a USB microphone, try a different USB connector. If the microphone came with software, make sure it is installed properly and is compatible with Windows Vista.
Step 3: Check volume levels and mute
The speaker volume for the microphone and line-in may be muted or turned down. Use the following steps to check the speaker volume levels for line-in and microphone.
1. Click to open the Sound Control Panel window.
2. Click Speakers, and then click Properties.
3. Click the Levels tab.
4. Click the Muted button next to any item that is muted.
5. Raise the level for each item to at least 50.
6. Click OK to save the new settings, and then close Speaker Properties.
7. Click OK to close the Sound Control Panel window..
Step 4: Configure Windows recording settings
By default, Windows Vista automatically enables microphones and line-in ports. Use the following steps to set the microphone/line-in port to be the default port and to configure the recording levels.
1. Click to open the Sound Recording window.
2. If multiple microphones or line-in ports are available, select the port that you want to use. Click Set Default to make this device the default audio input device.
3. If the device you want to use contains a small circle with an arrow pointing down, the device is disabled. To enable the device, right-click the device name and select Enable.
4. With the device selected, click Properties, and then click the Levels tab.
5. Adjust the slider to 75% of its range.
6. If Mute is on, click the Muted button button to unmute the device.
7. If Microphone Boost is available, adjust to +20.0 dB.
8. Click OK.
9. Test the microphone as was done in step 1 to determine if Windows is able to detect a signal for the microphone or line-in being used. If you have performed all the steps and the microphone or source device still does not work, the audio ports or sound hardware on the computer may be bad.
One other thing I mentioned before is this (following snippet) of a Microsoft Fixit troubleshooter that should be available on your computer. If it is, it can't hurt to try it.
Good Luck!!!
Sorry about the snippets which were jpg's, for some reason they would not paste here.