I heard somewhere (so probably not true) that the vista was originally based on windows 2000 or ME (cant remember) and Windows 7 is based on XP
Indeed. Allow me to give you a little history lesson:
Apart from the early beginnings (Commodore 64 Microsoft BASIC) the Bloodlines of MS OS's are these:
DOS (Monolithic real mode Kernel)
-> Windows 1.x - 3.0 (GUI on top of DOS)
-> Windows 3.11 (Several Enhancements to the Kernel, Protected Mode, 32bit PE support)
-> Windows 95 - ME (and then it became extinct, rightfully so with a degenerate last effort, if you'd ask me)
Windows NT 3.1 (Microkernel-Like architecture)
-> NT4
-> 2000
-> XP (2000 with enhanced GUI (uxtheme.dll), new NTFS revision, Activation)
-> Vista (Another new GUI, several driver related Kernel changes)
-> 7 (dunno, haven't looked at the changes yet.)