If Windows Updates doesn't deliver one, install the latest sound driver
and any software package given on the Support Downloads webage for your PC model.
You own a license for the Windows 7 version which came preinstalled on the new PC for it's life, to reinstall as often as you want. Was the Windows 7 copy on your older PC genuine? If not you should only reinstall the licensed version on the new HD following the Clean Reinstall tutorial.