Thin Client OEMs implement Windows XP Embedded's Enhanced Write Filter (EWF) tool to prevent write actions (and, therefore, flash-erase cycles) to the flash drive. All write actions are instead re-directed to the RAM disk (also known as the overlay).
To make any changes to the OS, such as domain connectivity or a TCP/IP static address change, you can disable EWF to allow the update to occur, and then re-enable it.
more you can read here http://msdn.microsoft.com/en-us/library/dd143259%28v=winembedded.5%29.aspx
Only Administrator accounts can access EWFMGR.EXE and the EWF API. Power User, User, and Guest accounts cannot change the state of EWF.
As an example, after you have set up your IP address and/or other system settings, you can try to run this command.
ewfmgr c: -commitanddisable -live
This commits all current level data in the overlay to the protected volume and disables the overlay.
The overlay is written to the protected volume on the next system boot. Committing the overlay can impact the speed of the boot process.
You can use the -live command for both EWF RAM and EWF RAM Reg modes to immediately commit the overlay to the protected volume and disable the overlay without having to reboot the system.
To disable EWF:
ewfmgr disk: -disable, however be aware, the longevity of flash drives is an issue, though. Both Windows XP Pro and Windows XP Embedded constantly read from and write to a disk, resulting in numerous flash erase cycles. Because both CompactFlash and mini-IDE flash drives have a limited number of these cycles, they wear out more quickly than they would if used as they would in a normal commercial environment.
More about commands/options you can read here: http://msdn.microsoft.com/en-us/library/ms940853%28v=winembedded.5%29.aspx