[gguruusa]

That's thread's kind of overkill for most WM6 users. It was written back in the early days.

The ext_rom holds additional applications, files, and registry settings your carrier customizes your phone with. Some of them are useful, mostly it's crapware. The good parts were extracted and bundled into the carrier OEMs in the kitchen, or if it's a useful application, into an OEM. All of this makes the original ext_rom contents pretty much useless (and problematic in the case of some files and registry settings).

To back it up, just unhide and copy the contents off using. Or, you can always extract the ext_rom image from your carriers ROM update - then you can flash it back any time you want. But it's only useful for educational purposes or returning your phone to stock.