Since a few months I've had some probs with a HP DV6700 type laptop. All of a sudden network stopped working, as did sound. Reinstalled Windows XP, and tried to find all the drivers. After some tinkering sound worked, and so did network. But after a few restarts, or a few days either sound or network, or both stopped working again.
A week ago installed Windows 7, which I hoped would solve things with correct drivers. However, the same problems occur. Network/sound were working after install, however they both stopped working after a few days. Sometimes sound would be there on restart, but after 10 mins it would suddenly stop working.
Today configured a new router, which works on my fixed PC. Wired network still not working on laptop. Wireless can connect, and gets inet connection, but this fails after a few seconds, and reconnects now and then. Also today all of a sudden sound worked again, and then failed again after another restart.
I had an HP tx1000 laptop that did similar things before it died. What may be happening is that it is running too hot and it is frying the motherboard, especially the connections to the wireless card. If I were you and if it is still under warranty, I would send it in to HP and get it corrected ASAP. If it isn't under warranty, find a computer repair service that is familiar with the problem.