Hi,
Could you please answer this below question?
a) Did you set iTunes as your default player earlier?
b) From when are you facing this issue?
c) Did you do any recent changes on your computer?
I recommend you to follow these below steps to set itunes as default player on your computer.
iTunes for Windows can be configured as the default application using the Default Programs control panel.
Changing the default media application
1.From the Start button, click Default Programs.
The Default Programs control panel appears.
2.Select Set your default programs.
3.Select iTunes.
4.To make iTunes the default player of all media types iTunes can recognize: Select "Set this program as default."
To customize which media types iTunes will play by default: Select "Choose Defaults for this program," and place check marks by the desired file types.
5.Click OK.
Note: To make a different application the default media player, follow these same steps and select the application you want to use. iTunes for Windows can be configured to notify you if iTunes is not the default player for audio files.
Setting notification if iTunes is not the default media application for audio files
1.Open iTunes.
2.From the Edit menu, choose Preferences.
3.Click the Advanced button and then click the General tab.
4.Click "Warn me if iTunes is not the default player for audio files" to select this option.
5.Click OK.
Each time you start iTunes, you will see this message: “iTunes has detected that it is not the default player for audio files. Would you like to go to the Default Programs control panel to fix this?” This message will appear unless iTunes is set as the default application. You can also unset this message.
Unsetting notification if iTunes is not the default media application for audio files
1.Open iTunes.
2.From the Edit menu, choose Preferences.
3.Click the Advanced button and then click the General tab.
4.Click "Warn me if iTunes is not the default player for audio files" to deselect this option.
5.Click OK.
For more information on this you may visit this below link.
http://support.apple.com/kb/HT3202
Thanks and Regards:
I. Suuresh Kumar- Microsoft Support.
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