Windows Embedded for HP Thin Clients - Write Filter Best Practices
5 
Registry filtering 
Caution 
HP does not support or recommend attempting to persist registry changes through write filters, as Windows is very 
complex and dependencies are not always clear. Usage of the Registry Exclusion List built into UWF or of the Registry Filter 
tool by Microsoft is at your own risk. 
The Registry Filter is a tool by Microsoft included in the Windows Embedded operating systems to help persist registry 
changes through write filters. However, not all keys are supported. HKCU settings are not supported. Microsoft supports 
only two default settings (TSCAL & Domain Secrets), but does not support custom implementations by an OEM. Registry 
Filter documentation is limited, and limitations on registry key/branch size and the number of entries were not documented. 
Monitored keys might not be written through if changes are made before the Registry Filter initializes on boot. Changes are 
only written during a graceful shutdown. 






