How to disable the Windows8 volume On-Screen-Display?

Here is a picture of what i am talking about.

I am at my wits end with that annoying thing, please somebody help me.

I have no idea why the moderator random deleted the working solution. There is a small tool called HideVolumeOSD which can hide the overlay:

To hide the volume OSD you can select the menu item “Hide Volume OSD” or just click on the tray Icon.

With this item you can toggle between visible and hidden volume OSD. If you exit the application, the volume OSD is always restored to visible state.

You can download it here and the sourcecode can be found on github

You can use Volume Step Adjuster to achieve this. I couldn't find a way to do this without using any third party software.

1. Download Volume Step Adjuster archive file and unzip it to a directory of your choice
   
2. Edit volstep_START.bat so the script asks to be elevated on execution
3. Edit volstep_STOP.bat and make similar changes
4. Add a shortcut to volstep_START.bat to the startup folder

REM Script name: volstep_START.bat
@echo off
:checkPrivileges 
NET FILE 1>NUL 2>NUL
if '%errorlevel%' == '0' ( goto gotPrivileges ) else ( goto getPrivileges ) 

:getPrivileges 
if '%1'=='ELEV' (shift & goto gotPrivileges)  
ECHO. 
ECHO **************************************
ECHO Invoking UAC for Privilege Escalation 
ECHO **************************************

setlocal DisableDelayedExpansion
set "batchPath=%~0"
setlocal EnableDelayedExpansion
ECHO Set UAC = CreateObject^("Shell.Application"^) > "%temp%\OEgetPrivileges.vbs" 
ECHO UAC.ShellExecute "!batchPath!", "ELEV", "", "runas", 1 >> "%temp%\OEgetPrivileges.vbs" 
"%temp%\OEgetPrivileges.vbs" 
exit /B 

:gotPrivileges 
::::::::::::::::::::::::::::
::START
::::::::::::::::::::::::::::
setlocal & pushd .

SET VOLUME_STEP=0.5
reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v volstep /f /t REG_SZ /d "\"%~dp0volstep.exe\" %VOLUME_STEP%"
cd /d "%~dp0" ← make sure you don't forget this line 
start volstep %VOLUME_STEP%

One way to fix your problem I found mentioned on TechNet's forums is a 3rd-party app available at DeviantArt.

Volume² is an advanced Windows volume control, a complete replacement for the standard Volume Control. This application lets you easily change the sound volume just by rotating the mouse wheel or by using keyboard hot keys or just mouse move on screen border. It includes an audio mixer with advanced volume controls support, a scheduler, an on-screen display, command line support, the ability to store and recall different unlimited presets via one mouse click or system-wide hot keys.