Open IIS
double click your PC name under Connections
Click Application Pools
Select your app pool (DefaultAppPool)
Then under actions on the right click Advanced Settings,

    Go to Process Model section and
    click on Identity. 

go to iis -> application pools -> find your application pool used in application -> click it and then click 'Advance Settings' in Actions panel. Find 'Identity' property and change it to localsystem.
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