I recently upgrade a HP dc700 to Windows 7 Enterprise and next thing I know there was no audio. The speaker icon will show a X and the tool tip said “No Audio Output Device”. I did all the typical stuff (download drivers from HP, manufacturer, run troubleshooter, etc) and still have no audio. If this is you, don’t be alarmed. There may still be one thing left to do. I resolved this issue by accessing the BIOS by restating the computer and pressing F10. Locate On Board Devices and Enable On Board Audio. Yes, it was that simple. Let me know if it works for you.