it's an HP Pavillion dv6711TX, i purchased it in 2008. it came with vista. i installed full version of windows 7 after the vista OS was corrupted. control panel shows that the sound driver is OK, but i only have the speaker working not the microphone.
What about the microphone? Did you just get a new one? Is it an old one? Have you checked to make sure you plugged it into the right plugin (can be harder than you think.) Also, how are you trying to test it? Windows sound recorder?
Almost sounds like the manufacturer didn't add support for the microphone. I'm guessing you have updated to the latest driver. You could run scandisk or chkdsk in the command prompt and just make sure everything is alright when the driver is being read from the hard drive.
Press "Win+R" to "Run" and typed "devmgmt.msc" (without quotes, of course), scrolled down to "Sound, video and game controllers," Right-clicked on "High Definition Audio Device," click "Uninstall," Reboot the laptop, Windows 7 automatically detects new device "High Definition Audio Device," subsequently installs the device driver, then "right-click" on the "Speaker" icon in the system tray, click"Recording devices," highlight the "Device default," click "Properties," clicked "Levels" and put both Microphone and Microphone boost to the maximum.