Over the years I have reinstalled Windows on many machines and when I have I have had trouble the most with drivers for two components more than any other, Video cards and sound cards.
If you have a chance to see the drivers on a Windows XP machine before you reload Windows it is always a good idea to make sure that you right click on the “My Computer” go to manage and to device manager and take a look and probably write down each of those components. This way if Windows can not find the component when you reload Windows at least you can go and try to find it yourself.
If you are stuck now though and have a computer with a build in Sound cards and you would like to try to find a sound card driver than you can do what I tried successfully tonight, download an AC97 sound card driver and try that. If you can find the driver than it is just a case of running the install or setup.exe file and then after you are done you can reboot the computer and you will hopefully have sound again.
If this does not work then one of the things that you can do is to do a Google search for the computer model that you have and add sound driver to the query or you can actually open up the case and see if there is any reference to the motherboards or, if you have a sound card that is plugged into a slot look for the type of card that it is.