Open your registry and find the key below. 

Create a new DWORD value named "NoLowDiskSpaceChecks" and set the value to "1" to disable the warnings 

Key:[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
Value Name: NoLowDiskSpaceChecks
Data Type: REG_DWORD
Data:(1 = enabled)

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