Quote Originally Posted by PeterHallowe View Post
1) Etrex 20, WebUpdater says that it is uptodate, ID ......
That's not your device's HWID, it's the UID (Unit ID). You should edit your post to remove it as it's not something you should disclose publicly.

2) I disabled the UK Openstreetmap and enabled Worldwide AutoRoute DEM. Switched off and now it will not restart.
"Worldwide AutoRoute DEM" is an automotive device basemap. I don't think it's an OEM map for eTrex. As it seems from your answer to "5" that you still have Mass Storage Mode available you might solve your problem by simply removing that map.