ive had this laptop for over a year and a half now, about a week ago out of nowhere my sound just stopped working and there is a red cross over the sound icon in the taskbar and when i hover over it it says 'no audio output device is installed'. the sound is now a bit hit and miss, sometimes it will work for a little bit after its been in sleep mode or has been rebooted but the sound cuts out again after a little while. ive tried re-installing the drivers and downloading them again from the website but that doesnt work and have tried a system restore to when it worked before but no change. also the sound part in the device manager has disappeared. does anybody know how to fix this?