Go to the hp website www.hp.com
on the dv4000 computer. Enter dv4000 and then the sub model number on the label from the bottom of the laptop. Then allow the installation of the driver scanner from HP to download/install (press OK to continue to install and let it scan the unit for needed driver updates), then go to the Audio section of the then listed drivers. after entering the operating system installed (see Start>Control Panel>System>General tab for installed OS info), and install that latest Audio driver package update. I would also personally install all the other required driver(s) & the latest BIOS update listed there also myself. IMPORTANT: When installing the latest released (or highest #'d) BIOS update (the BIOS simply allows all the hardware to work together w/ the OS), make sure the computer is plugged in, and do not interrupt the install process or restart/shut down the unit until the program does it for you. (If you have never "flashed a BIOS" before...Have a techie friend do it for you instead, after downloading the proper file/& flash utility...Real patience pays here, or you can flat turn a motherboard into a useless doorstop). It can always be reflashed by the manufacturer (or others), though even if a BIOS Flash is messed up.
Free Belarc Advisor (www.belarc.com
) if installed and run will inventory all your hardware & software if you have any questions about whether a specific driver listed matches your specific hardware concerning that dv4000.
There were a few HP dv series laptop motherboards that had a problem holding both Video & Audio drivers (install 1 and the other would blow out & get corrupted), install the other and just the opposite...They had a class action settlement that was only 90 days or 6 months long and really screwed many of us over in the process. If there is a choice between the dv4, dv6, & dv7 series I always pick the dv7 series to recommend to & for my customers.