The Win7PE SE project base includes only a minimum of applications. Take pleasure in personalizing it by adding your own applications scripts and other utilities. Here are some possibilities.
Get the Realtek High Definition Audio Driver x86/x64 and extract to the \Projects\Win7PESE\Drivers\ folder.
Drivers from Driverpacks.net may be used in conjunction with the Win7PESE->Drivers->Driver Integration & Driver Package Installer script.