Win10 is supposed to be compatible back to Office 2007, but not with 'Office Starter 2010'. It's incompatible with Office 2003 and XP. I thought that it checked compatibility as part if the upgrade but I don't remember. My wife uses LibreOffice which is free.

Win 10 did reset the default picture viewer as mentioned by Bill D - which was annoying, but the new one works OK so I left it.

I read that if you get adverts on the lock screen you can turn them off.