I seem to have lost the drivers for my sound card. The speakers started to make a strange sound followed by them not now working at all. In Device Manager a yellow question mark appears before Multimedia Audio Controller and a yellow exclamation mark appears before each of the audio devices under Sound, video and game controllers (please see below). Please help, how can I restore the drivers for these devices including one called ac97 which seems to be missing from the device manager list as I know it has been there in the past?

Other devices
Multimedia Audio Controller

Sound, video and game controllers
Audio Codecs
Legacy Audio Drivers
Legacy Video Capture Devices
Media Control Devices
Microsoft Kernel Acoustic Echo Canceller
Microsoft Kernel Audio Splitter
Microsoft Kernel DLS Synthesizer
Microsoft Kernel DRM Audio Descrambler
Microsoft Kernel GS Wavetable Synthesizer
Microsoft Kernel System Audio Device
Microsoft Kernel Wave Audio Mixer
Video Codecs

Usually, drivers for your specific operating system version will be available on the web site of either A) your motherboard manufacturer (for integrated audio), or B) the manufacturer of your audio adapter (for discrete audio). Post motherboard model or audio adapter model for additional info.

Right click on the Multimedia Audio Controller and right click and choose "delete' on say OK

Close all windows and then restart computer - check your devices again, windows should install them on reboot

Post back with info posted above if this does not help