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Windows XPE Enhanced Write Filter header conversion

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v1.2 - 26 Nov 2018
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 Windows XP Embedded Enhanced Write Filter (EWF) is used to protect one or more disk volumes by intercepting write requests to the volume and redirecting it to an overlay volume, either RAM or another disk. Note the EWF header conversion is only useful on Windows XP Embedded with the Enhanced Write Filter DLL installed. It is not available on Windows XP Pro, or other operating systems.

EWF is designed to protect the Windows boot volume so effectively it's write protected and boots up identically each time, with any changes made to a protected drive being lost on power down. If changes need to be saved, EWF API calls are needed followed by a reboot to actually update the protected drive.

Microsoft provides a command line utility EWFMGR.EXE that reports any protected volumes and provides various commands that will be processed on the next restart of the PC.

The EWF API allows these commands to be made from Windows applications. The Microsoft EWFAPI.H C header file is included, with the Microsoft help file that details the various APIs. The EWF API functions enable applications to query and modify EWF configuration settings for protected volumes. Typical usage scenarios for these functions include:

- Disabling/enabling EWF for a protected volume.
- Restoring or discarding an overlay level.
- Creating a checkpoint by adding an overlay level.
- Committing the current overlay.
- Persisting data through a reboot.

As well as a Delphi conversion of the EWF APIs, this package includes a Windows demonstration application using the APIs. Please note this program has only been testing on Windows WP Embedded running on a flash memory C drive (IDE interface) with a single overlay in RAM. It has not been tested with a hard disk which potentially offer multiple overlays.

Release Notes

1.0 - 20th October 2005 - baseline
1.1 - 5th August 2008 - updated to be compatible with Delphi 2009
1.2 - 8th April 2009 - added MINENUMSIZE 4 so that enumerated variables are correct length for C++, thanks to Sven van Bruegge. This fix means the protected info should now be correct.

Demonstration Application

A Windows demonstration application XPETEST.EXE is supplied, with source and compiled program. When started, it displays information about any protected drives found, and provides buttons to Disable Overlay, Enable Overlay, Commit Overlay, Save Persistent data and Clear Command.

Compatible with Delphi 7/2006/2007/2009/2010/XE/XE2/XE3, only useful on Windows XP Embedded with EWF installed but may be compiled or run on Windows 2000 and later.

Windows XP Embedded Enhanced Write Filter header conversion is copyright by Magenta Systems Ltd, but may be used freely.

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Phone 020 8656 3636, International Phone +44 20 8656 3636
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