Sarah,
It's possible that the drivers may be on the CD you have. However, we would recommend you try the below recommendations. Because the sound card has worked in the past in Windows XP it is likely it already has the drivers and that it is compatible with Windows XP.
Open Device manager and see if any “sound, video, and game controllers” listed. If so Click the “+” sign and remove any sound video game controllers. In addition if you have any “Other Devices” remove any of these devices as well. Additional information and help with getting into the device manager can be found in the below document.
http://www.computerhope.com/win95er.htmOnce this has been completed attempt to reboot the computer and see if Windows re-detects the sound card. It is likely that it may ask for the drivers if it is unable to find compatible drivers. If this occurs attempt to insert the CD you have and/or you’re Windows XP CD if you have one of these. This should hopefully reinstall your Sound card.
If this does not resolve your issue try visiting the below Microsoft windows update site, often Microsoft will updates for computer hardware devices on the update page. Additional information about updating Microsoft Windows can be found on the below link.
http://www.computerhope.com/issues/ch000545.htmFinally if this still does not resolve your issue you will need to determine the type of sound card you have in the computer and/or attempt to download the sound drivers from E-Machines. A listing of sound drivers can also be found on the below link.
http://www.computerhope.com/drivers/sound.htm