Unwanted defaulting to desktop

I've finally had enough and need help! For some time now whenever I close a Metro App (are they still called that?) my machine defaults back to the desktop , even if I have other Metro Apps open. It boots to the Start Screen ok and I want it to stay there until I tell it otherwise! anybody know how to make it behave please? (It's a Samsung all-in-one deskto with Norton 360 anti-virus).

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 8.1, 64 bit
Processor: Intel(R) Core(TM) i3-3220T CPU @ 2.80GHz, Intel64 Family 6 Model 58 Stepping 9
Processor Count: 4
RAM: 3983 Mb
Graphics Card: Mirage Driver
Hard Drives: C: Total - 927684 MB, Free - 851915 MB;
Motherboard: SAMSUNG ELECTRONICS CO., LTD., DP700A3D-A05UK
Antivirus: Windows Defender, Disabled