As the error message says, if you get Error 740
PS C:\Users\matty> DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:z:\sources\sxs Error: 740 Elevated permissions are required to run DISM. Use an elevated command prompt to complete these tasks.
…you just have to run your Command Prompt or Powershell window ‘as Administrator’. i.e. right-click on the icon and select ‘Run as administrator’
PS C:\Windows\system32> DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:z:\sources\sxs Deployment Image Servicing and Management tool Version: 6.3.9600.17031 Image Version: 6.3.9600.17031 Enabling feature(s) [==========================100.0%==========================] The operation completed successfully. PS C:\Windows\system32>