I have an old program(business) which only works in XP or Vista so i installed VISTA PRO from a disc on my older (12y old) PC E-Machine AMD Athlon II X2 Dual Core 6gb RAM with 2 HDs and Windows10(originaly W7). Vista was installed on the second HD (500 gb) W10 was on the first HD(2TB). Vista PRO insallation was perfect and after SP2 installation everything worked fine including my old program too. Unfortunately the dual booting doesn't work as i expected. It boot only boot in Vista even if i go to F12 and enter in the boot seq. menu indicating booting from my first HD it will allways boot from the second HD where Vista is located. I red that if you install and older OS after W10 even if it is installed on a different HD it will change the MBR and you can't boot in to your W10 OS even if that is not on the same drive. What should i do? I am sure there must be a fix for this problem.