Usually, a new version of an operating system changes existing features and adds new ones, but sometimes the changes mean that old features aren't available any more. The full-screen Start screen of Windows 8.1 isn't the only casualty and you can make the new Start menu bigger, although you can't bring back the full-screen list of installed apps, just the big view of pinned tiles.Software and hardware compatibility is good with Windows 10; elderly applications should still work. As usual, you're going to need new versions of security and anti-virus software, and probably of most system-level tools (although handy utilities like ClipMate and WinDirStat continue to work without any problems).

The Windows 10 advert you'll have seen on your PC that lets you reserve your free upgrade also performs a compatibility check, so it will warn you of any software or peripherals that won't work with Windows 10. For example USB floppy drives will need a new driver (there's one on Windows Update that works with most models).