Problems with WinXP Pro

Alright, I'm alright with computers but not the greatest so bear with me just a little bit here.

I recently installed a hard drive on computer and installed Windows XP Pro on the machine.  So far, it's been running fine, it boots up quick, it works great...but my problem is that it doesn't recognize any of the hardware...so I don't have any sound.  I only found this out when I tried to play some music using Windows Media Player and I got an error prompt saying that no soundcard was detected.

What can I do?

>>5
Registering XP online will do nothing. You simply need to work out what devices it can't find drivers for in the other devices category in Device Manager, find out the manufacturer and model number, and get appropriate drivers from the official websites or driverguide.com.