HP XW4600 - Speaker icon has an "X" and says no speakers plugged in. The internal speaker is connected on the motherboard. Control panel "Sound" window shows High Definition Audio Device under playback but says not plugged in and doesn't show speaker icon in this box (as it shows on a similar HP box running Windows 7). Scanned for hardware changes but I can't enable the internal speaker! This used to work and the only thing I changed was a video card.