Supposedly you can boot 64 bit Vista or Windows 7 from a GPT disk on a UEFI system(which is what Windows 10 uses) but I have never done it. It may be easier to have a HD tray quick release where you slide the HD out like a drawer and slide the other one in. Then change the boot type to MBR/legacy or UEFI. Again I haven't done it but maybe somebody else has. Also I would ask on Windows 10 Forums since it has much higher traffic than here.
Thanks bro i am now installing vista but teh problem is i deleted system reserved prt during installion. Now how can i dual boot vista and 10. Start pc with windows 10 usb and repair start up ? Can you help please
The system needs to boot using UEFI to boot both from the same HD. I have never done it so I have no experience to share. I am sure somebody on Windows 10 Forums is multi-booting W10 with older OS.