I have a Dell Inspiron 6000 laptop. I had formatted the system as it was working slow. I installed Windows XP back again. After installation I added drivers and quired codec. It looks the system is not working fine. There is a problem with mic. There is no audio on the system. I installed the codec again but still the same issue. The audio card does not help much.
Go in Device Manager. There you would be able to see which hardware is installed and which is not. You can right click on the same and choose update. If that does not work then simply uninstall. Then restart your system. On reboot it will detect and install the same.
You just need the right motherboard drivers for that. You can check that on the official website. Dell offers all drivers instantly on the official site. After driver installation it is recommended that you run Windows Update also. It will fix up all issue with codec and other stuff.