i realized that i don't understand how buying or upgrading operating systems work

[thatguyfosho]

Okay. So I have my current computer, an old crappy Dell which I've slightly upgraded, and my new one which as of now is unbuilt (some parts are still coming in). My Dell has Vista Home Premium 64-bit, and I have not yet purchased an OS for my new computer, quite frankly, because I'm confused. Trying to resolve that, I was browsing newegg when I noticed Microsoft Windows 7 Home Premium SP1 64-bit - OEM for $100 and I thought "Hm, I guess this is what I need?" but then I saw Microsoft Windows 7 Home Premium for $200 and then I thought "Fuck." What's the difference between the two? And is it possible for me to upgrade my Vista to 7 on this computer (isn't that supposed to be cheaper?), then transfer it my new one?

Thanks.