Laptop Won't Complete Windows Launch

Got a new Dell laptop today that came with W10 pre loaded. Have installed dropbox, and spotify and AVG. Rebooted it a couple of times during all this and all seemed fine.

Now when it is switched on it shows the login screen and I enter the microsoft account password. It shows the desktop wallpaper, and the desktop icons, but it does not show the taskbar icons or the clock in the notification area. It shows the mouse pointer, which can be moved with the touchpad, but neither left nor right mouse buttons have any effect. The keyboard is unresponsive (despite working 5 seconds earlier to enter the password) so Alt-F4, Ctrl Alt Del and Windows key have no effect.

If the pointer is moved down to the taskbar it changes from the default arrow to the 'busy' circle, but after leaving it for half an hour or so, there is no progress. The only route I have found out of this is to hold the power button down to force a shutdown. When I power it back on the login screen appears, and I can move the cursor, type etc and everything seems normal. When I enter the password and login, I get the same thing again - wallpaper, desktop icons, but no clock and then no further response.

I got into safe mode and selected 'recover from restore point'. This failed (when did it ever work!?!). The laptop rebooted and then went straight into the initial reload i.e. asked for country, language, keyboard type, etc etc seems I have lost everything.