Found it! There's a registry key for 'active probing', which is being blocked by our network.

The answer is is a post on the Stack Exchange SuperUser site, so rather than steal their glory here's...

Fixed it - for anyone else who hits the same issue, it was the changes installing the AU had made to the settings in
Settings >> Privacy >> Background apps

Edge was set as running in the...

The plot thickens - I did my home machine by the same route and don't get this issue.

We're currently looking at whether there's something going on around detecting the wireless network (despite...

Thanks!

From your excellent list of suggestions

a) - yes, still happens
b) - cannot see anything out of the ordinary, nor any reason in there why the browser would open
c) - yes, still...

We recently updated two machines to the Anniversary Update (via the Media Creation Tool method).

Since the update, when you log in, the default browser is automatically opened at MSN.com. Neither...

You can create a 64 bit disk from the 32 bit version of the Media Creation Tool (which is the only version you'll ever get to run on your 32 bit machine).

Just follow the instructions in Option...