Hi Prabha2u.tsm,
1. Have you made any recent changes on the computer?
2. Do you have any security software installed on the computer?
Method 1
a) Click on Start and in the search bar type cmd.exe
b) Right click on cmd.exe and click on Run as Administrator
c) In the command prompt type the following command
net localgroup "Administrators" "NT Authority\Local Service" /add
d) Press enter and restart the computer
e) Check if you are able to play the files in Windows media player.
Method 2
Uninstalling and Reinstalling the Windows Media Player:
Uninstalling the Windows Media Player:
a) Go to Start and in the search type "Turn Windows features On or Off"
b) Click on "Turn Windows features On or Off"
c) Browse to the Media Features and uncheck the mark in front of Windows Media Player.
d) Restart the computer
Reinstalling the Windows Media Player:
a) Go to Start and in the search type "Turn Windows features On or Off"
b) Click on "Turn Windows features On or Off"
c) Browse to the Media Features and place a check mark in front of Windows Media Player.
d) Restart the Computer.
Try playing the file now.
Method 3
If the above step fails then run the Windows media player troubleshooter and check.
Open the Windows Media Player Settings troubleshooter
http://windows.microsoft.com/en-US/windows7/Open-the-Windows-Media-Player-Settings-troubleshooter
Hope this helps!
Halima S - Microsoft Support.
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