You may encounter an error while trying to sign on to MSN Messenger: Error 81000306. There are various possible reasons for this error message. Some of them are listed below:

1. Your internet connectivity may be lost or could be intermittent
2. The messenger service may be temporarily unavailable
3. There may be some entries in the Proxy settings which may be blocing the messenger accesss
4. The “Auto Tuning” feature for networking in Windows Vista may be interrupting the messenger access
5. The wireless/wired router may be blocing the connectivity

To resolve this issue, follow the steps below

1. Check if you have internet connectivity. For this you can try accessing some websites and if they show up, the internet is working properly. If the internet is not working, please speak to your Internet Service Provider (ISP) to restore connectivity.

2. To check availability of the messenger service, go to http://windowslive.com/desktop/messenger to check if there is any notification on non-availability of the service. Though this is highly unlikely, but still wortch checking before you continue any further to resolve the situation at hand.

3. Check for “Proxy Settings” in your Microsoft Windows Live Messenger settings. Ideally, there should be none. To check this, perform the following steps:
 
 a. On the Windows Live Messenger sign-on window, click on “Tools” and then on the pop-up menu, click on “Options”. If this option is not available on your messenger     screen, click on the blue question mark to get a drop down menu. On this menu, click on “Show the Menu Bar”. This will make the options visible on the top of the     messenger window.
 b. On the screen, click on “Connection” on the left panel of the active window and then click on “Advanced Settings” button in the “Connection Settings” segment
 c. This will open a new “Settings” window. On this window, the “SOCKS” text box should be blank. If it isn’t, delete the string in the box. If there were some entries in the box, click on “OK” button twice and then try to sign in again. If the box was empty, continue to the next step.

**Please note that the next step applies only if you are using Windows Vista**

4. Click on the “Start” button and go to “All Programs”. Click on “Accessories” folder and Right click on “Command Prompt”. On the pop up menu, click on “Run As Administrator”. Click on “Yes” on the subsequent window to allow launch of Command Prompt in Administrator mode. Now type in the following command:

netsh interface tcp set global autotuninglevel=disabled

Now press “Enter” on the keyboard.

Now try to sign in to messenger again. If it does not work, go back to the  Command Prompt window and enable Network Auto Tuning feature by typing the command below:

netsh interface tcp set global autotuninglevel=enabled

Now close the Command Prompt window.

Your Microsoft Windows Defender protection tool may report error 0×80070003. This is primarily due to Windows Installer issues, where the updates and patches are not getting installed properly. To resolve this issue, you should follow the steps below:

1. Log in to your computer as an “Administrator”

2. Run Windows Update and install all updates

3. Verify that all the updates are installed properly

4. Download and then install the latest version of Windows Installer (4.5) from the following link:

http://www.microsoft.com/downloads/details.aspx?FamilyID=5a58b56f-60b6-4412-95b9-54d056d6f9f4&displaylang=en

5.  Download the Windows Installer cleanup utility from the link below. This will clean up any entries for failed installations on your computer and will allow troublefree installation of updates and patches.

http://www.softpedia.com/get/Security/Secure-cleaning/Windows-Installer-CleanUp-Utility.shtml

6. Now reinstall Windows Defender and run the Windows update again