Even if it doesn't ask, a reboot helps Windows 7 properly "handshake" with the new hardware.
Go to the motherboard manufacturer’s site (ASUS, Gigabyte, MSI) or the audio chip maker’s site (Realtek is the most common). Option B: Realtek High Definition Audio Codecs pc speaker driver windows 7 download
Open the , right-click Computer , and select Manage . Click Device Manager on the left. Even if it doesn't ask, a reboot helps