I reinstalled win xp on my Dell laptop. I have no sound and an asteric next to IDT high definition codec.?

When you uninstall your operating system then reinstall, Most of your computer drivers will not be on the PC. So what you need to do is go to Dell's support website an search for the appropriate driver for your model of laptop, Then install it and the sound will work. That goes for all devices that show up unknown on your device manager.