Upgrading Win7 to Win10 on a dual boot WinXP/Win7 system

[Imacflier]

My current system is a dual boot system: WinXP SP2 and Win7 Ultimate x64. I want to end up with a dual boot system of WinXP and Win10 (I have CAD software which will not run under Win 7 and I cannot afford the upgrade cost at the moment). If I just run Windows update after booting to Win7 what happens?

 

[StarXeon]

Sorry. I don't quite understand. What exactly are you asking? Are you asking what will happen if you run the windows 10 update?

 

[Imacflier]

Yes, that is exactly my question.