Confused about Windows 7 OEM

I am getting Windows 7 Home Premium 64 Bit for replacing my Windows Vista Home Premium 64 Bit .
my concern is this... When I looked into OEMs of Windows OS's it mentions how the operating system ties to whatever motherboard it was installed on at the time of installation.
well call be crazy but isnt that not the case? i mean to paint a picture of my situation i am putting this Operating System on a Pre-built Dell that runs on the First Gen Core i7 (Socket LGA 1366) and is runnning with 6 gigs of DDR3 RAM along side an ATI Radeon 4600 card. Given all of the information you can take two things away from this. one being that trying to find a socket LGA 1366 with PCIe 3.0 is gonna be hard as hell to find seeing as i would want a nice PCIe 3.0 graphics card to compliment my First Gen i7. and the other being that the explanation i get about OEM OS's confuses the hell out of me to no end. to sum it up i need someone to explain it to me in a decent way.  

prebuilt with vista that means vista is tied to that mobo you can install over it no problem. windows 7 will think nothing of it and ask for its' validation code.

but if i swap out the CPU and motherboard out with a new one will i be able to use the same key/disc for Win 7 or will i need a new one?

I have been using the same windows 7 OEM key for a couple years now.  I used the same key every time.  This last time I changed my motherboard and I had to call a 1 800 number and enter a set of numeric codes on my screen.  Then the automated service gave me a set of numeric codes and I had to enter them.  This verified my windows as genuine windows.  

With all of the iterations of windows thus far, OEM installations have meant different things depending on where you see it. An original equipment manufacturer (OEM) will likely buy the rights to the licenses for individual installations of Windows, but they will usually create a custom ISO or image of their own filled with their own bloatware and whatnot. However, when you go to a store and you see a copy of Windows that says OEM, this simply means that it will not give you the option to upgrade, it instead will only allow you a fresh installation of Windows. Some rumor sites have been all aflutter over some vague rumor that Microsoft is working with companies to tether the OS to the motherboard of the device with a mod chip, thus far this endeaver has not proven fruitful, as there are no such examples on the open market (at least that I am aware of.)