[Note that this is related to the iPaq; I do not know details of other
hardware]

Excerpts from mail: 31-Jul-101 Re: Losing Wince? by Rasputin@submonkey.net 
> Ah, I had some wierd notion of lazily reading the WinCE ROM 
> image up a serial port to disk, then writing it back later.
>  
> But even if that were possible I expect the M$ legal ninjas
> would be on you like stink on a monkey...

Oh, you can restore Wince, definitely. There is a Wince app which sucks
the ROM out in 4MB blocks. The usual procedure is to dock your iPaq to a
Windows activesync host, run this code, copy the images files a chunk at
a time, erasing them from the iPaq as you go along. Many iPaqs don't
have enough RAM to store a copy of the entire ROM, since that's where it
appears if it's a file.

The problem here is that there is no real ROM bootloader. When you
install the linux/compaq research labs bootloader, you are replacing the
first code that gets executed when the CPU is turned on. If you replace
it with the wrong thing, you can not fix it on the device.

The bootloader that they use lets you format the flash into partitions,
lets you write protect blocks of flash, and do all sorts of useful stuff
via serial console on bootup. Once you have it in there and write
protected, you're in luck, and can replace the kernel without any risk.

Compaq Research Labs have also promised to recover and restore the flash
on any iPaq which has been killed due to an error in this process.

So, yes, you can backup and restore wince, it's just risky...

gopi.