Loss of sound

Hello. I'm looking for some assistance for a problem that has literally occured overnight. I am not exactly a computer noob but certainly no expert either. I have been using the computer for about 6 months with no problems. I was using it late Saturday night and there was nothing wrong with the sound. I turn it on and fire it up Sunday morning to see the speaker icon on the Taskbar has a little red cross along side it and a box telling me 'No Audio Output Device is Installed.' Having done nothing that could have affected the Audio Output I was a bit perplexed.I tried System Restore but that made no difference. I tried the Windows Help with the option to automatically fix the problem but it didn't. If I go into Control Panel…Hardware and Sound…Sound…Manage Audio Devices, I get a box with 'Digital Display Audio,AMD Audio Device,not plugged in'.If I right click on this I find 'Show Disabled Devices' and 'Show Disconnected Devices' both ticked.This seems to be the only Audio Device option I have. I'm pretty sure I used to see a Realtek icon on the Taskbar but there is'nt one there now although I do have a Realtek folder in my Programs but there is no exe file in there? I have no Realtek Audio Manager option anywhere on the computer. The system is Windows Vista Home Premium 32 bit OS, Intel Core 2 CPU, 4Gb RAM,AMD Radeon HD 6670 Graphics.In my Device Manager,Sound,video,Game Controllers, the only sound device listed is AMD High Definition Audio Device. Anyway I would be grateful for any advice or suggestions you could give me. Regards and thanks in advance.

OK. I reinstalled the Realtek driver and everything seems ok now.

I agree with Terry. Thanks for the follow-up. Someone else with the same problem may now benefit from your efforts, and more importantly, from you coming back and providing the solution. People helping people is what these forums are all about.

Thanks gentlemen. I knew if I couldn't sort it myself I would have got all the help I needed here. Regards Alan.

Some times, I have found just laying the problem out in front of me - as required when you create a post about the problem - lets me "see" the big picture better. Looks like that's what might have happened here with you. So bottom line, I am glad we could help. We spent so much time on your problem, I was afraid it was going to be unresolved! lol.

Well the problem is back.Turned the computer on this morning got same problem as described in my first post.I've tried a few things. Last week I installed a program called 'Game Booster' which shuts down stuff running in the background to help game speed etc. I uninstalled this program then reinstalled the Realtek drivers but no go. I next ran TFC and did full system scans with Malwarebytes and AVG. Malwarebytes found a Trojan called Winlock.Again reinstalling the Realtek drivers made no difference.Any help would be appreciated.

Now I'm really confused. Turned the computer back on after a few hours and the sound is back. Strange thing is I don't have the speaker icon on my taskbar but I do have the Realtek HD Audio Manager icon. Also the Realtek Digital Output option is back on the 'Manage Audio Devices' list