Hi dowsp,
The rootkit scan came out clean.

Well try to solve the audio problem using a registry fix.
The steps that I am about to suggest involve modifying the registry. Modifying the registry can be dangerous so we will make a backup of the registry first.
Modification of the registry can be EXTREMELY dangerous if you do not know exactly what you are doing so follow the steps that are listed below EXACTLY.
If you cannot perform some of these steps or if you have ANY questions please ask BEFORE proceeding.Backing Up Your Registry- Download ERUNT
(ERUNT (Emergency Recovery Utility NT) is a free program that allows you to keep a complete backup of your registry and restore it when needed.) - Install ERUNT by following the prompts
(use the default install settings but say no to the portion that asks you to add ERUNT to the start-up folder, if you like you can enable this option later) - Start ERUNT
(either by double clicking on the desktop icon or choosing to start the program at the end of the setup) - Choose a location for the backup
(the default location is C:\WINDOWS\ERDNT which is acceptable). - Make sure that at least the first two check boxes are ticked
- Press OK
- Press YES to create the folder.
Registry ModificationsPlease copy the entire contents of the codebox below into Notepad:
- Open Notepad (go to Start>Run and type in notepad.com)
- Copy the contents of the codebox below using CTRL+C (or selecting all the text in the box, and right clicking on it and selecting Copy)
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Drivers32]
"midimapper"="midimap.dll"
"msacm.imaadpcm"="imaadp32.acm"
"msacm.msadpcm"="msadp32.acm"
"msacm.msg711"="msg711.acm"
"msacm.msgsm610"="msgsm32.acm"
"msacm.trspch"="tssoft32.acm"
"vidc.cvid"="iccvid.dll"
"VIDC.I420"="i420vfw.dll"
"vidc.iv31"="ir32_32.dll"
"vidc.iv32"="ir32_32.dll"
"vidc.iv41"="ir41_32.ax"
"VIDC.IYUV"="iyuv_32.dll"
"vidc.mrle"="msrle32.dll"
"vidc.msvc"="msvidc32.dll"
"VIDC.YVYU"="msyuv.dll"
"wavemapper"="msacm32.drv"
"msacm.msg723"="msg723.acm"
"vidc.M263"="msh263.drv"
"vidc.M261"="msh261.drv"
"msacm.msaudio1"="msaud32.acm"
"msacm.sl_anet"="sl_anet.acm"
"msacm.iac2"="C:\\WINDOWS\\system32\\iac25_32.ax"
"vidc.iv50"="ir50_32.dll"
"wave"="wdmaud.drv"
"midi"="wdmaud.drv"
"mixer"="wdmaud.drv"
"VIDC.WMV3"="wmv9vcm.dll"
"VIDC.VP40"="vp4vfw.dll"
"msacm.voxacm160"="vct3216.acm"
"MSVideo"="vfwwdm32.dll"
"MSVideo8"="VfWWDM32.dll"
"wave1"="wdmaud.drv"
"midi1"="wdmaud.drv"
"mixer1"="wdmaud.drv"
"aux"="wdmaud.drv"
"vidc.VP70"="vp7vfw.dll"
"vidc.X264"="x264vfw.dll"
"VIDC.FPS1"="frapsvid.dll"
"vidc.VP60"="vp6vfw.dll"
"vidc.VP61"="vp6vfw.dll"
"vidc.VP62"="vp6vfw.dll"
"vidc.DIVX"="DivX.dll"
"VIDC.UYVY"="msyuv.dll"
"VIDC.YUY2"="msyuv.dll"
"VIDC.YVU9"="tsbyuv.dll"
"VIDC.DRAW"="DVIDEO.DLL"
"VIDC.YV12"="yv12vfw.dll"
"wave2"="wdmaud.drv"
"midi2"="wdmaud.drv"
"mixer2"="wdmaud.drv"
"aux1"="wdmaud.drv"
"wave3"="wdmaud.drv"
"midi3"="wdmaud.drv"
"mixer3"="wdmaud.drv"
"aux2"="wdmaud.drv"
"VIDC.MSUD"="msulvc05.dll"
"wave4"="wdmaud.drv"
"midi4"="wdmaud.drv"
"mixer4"="wdmaud.drv"
"aux3"="wdmaud.drv"
- Now return to Notepad and use CTRL + V (or rightclick on the whitespace and Paste) to paste the script
- Verify that you have pasted the complete script
- Save the Notepad file to your Desktop as audio.reg using Save as Type: All files
- Next, locate audio.reg that you saved on your desktop
- Double click to run, and when prompted Allow the file to merge with your registry.
After that, Reboot your machine
Test youtube if you can now hear sounds. Tell me how it goes.