Hello I just developed software on XP and later did check on win 7 and 
	just moment ago, the software failed on windows 10 64bit.
 
	I'm webdeveloper and this is first time developing windows software, 
	so here comes the question:  
	Is there platform to test software on all versions of windows?  
	One option that I used for webdevelop, was virtualbox and  
	download the all versions of windows:  https://developer.microsoft.com/en-us/microsoft-edge/tools/vms/ 
	but it seems that it doesn't work for programs only for browsers 
	(from point I checked, maybe I'm wrong).  
	So are there windows versions that are full and free of charge  
	to download and test it in virtualbox?  
	Or I need to get all windows licences?