The automatically saved settings file 'visual studio 2012\settings\CurrentSettings.vssettings' cannot be found. You can change this file on the 'Import and Export Settings' Tools Options page. The IDE will use your most recent settings for this session.

I moved my documents from d drive back to c and this is what I got in both Visual Studio 2012 and Microsoft SQL Server Management Studio

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Microsoft Visual Studio
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The automatically saved settings file 'visual studio 2012\settings\CurrentSettings.vssettings' cannot be found. You can change this file on the 'Import and Export Settings' Tools Options page. The IDE will use your most recent settings for this session.
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OK  
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Default empty string value for varchar columns in Microsoft SQL Management Studio

To insert empty string as a default value in SQL Management Studio you need to enter ('') (open parenthesis, two apostrophes, and close parenthesis) into 'Default Value or Binding' field.