Enabling Devices

I recently had to install a new hard drive because the
old on crashed and could not be recovered. Since the new
Western Digital 160GB has been installed I have no
sound. All the devices show they are there but in
troubleshooting when checking to see if they
are "enabled" the "device usage" window is blank and the
pull down menu cannot be accessed. How do I get this
window activated so I can enable the devices for my
integrated audio?