BleepingComputer.com: confused - "oem", "retail", "system builder"

I am in the process of building a new system and have chosen Win 7 as my OS. I still need to buy the OS, but I am confused about the terminology. I think that "retail" means a full version with all the support from microsoft. I posted previously and was told that the "system builder" was for a new machine and could not be transferred and that the builder was responsible for support. Does that mean that I can't call Microsoft if I have issues or use their online help? Is "OEM" the same as "system builder"? NewEgg has the system builder for just over $100, other sites have the OEM w/ full license (see outletpc.com) for about $120 and then Newegg again has the full retail for $190. I really would like to get by for one of the cheaper two.

Also, if I can (or should) use the system builder version, is it worth while to move up to the "professional" for another $33?

I am building a 64 bit system, for detail see my post in new builds.

Thanks!

OEM is the the same product as "system builder". The licence is tied to the hardware of the PC it's first installed on.

Two types of "Retail" exist, full retail and upgrade retail. The latter requires you to have a previous version of Windows installed or the CD/DVD available.

http://windows.microsoft.com/en-ca/windows7/products/compare

For students:
http://www.microsoft.com/canada/windows/di..._vanity_student
http://www.win741.com/

EDIT: Deleted unnecessary quote to reduce thread clutter. ~ Animal

So if I buy the system builder/oem version from newegg and install it on my new build it would be the same thing as if I bought a computer at a retail store that had Win7 all ready loaded on it? I guess with the exception of having a disc in hand versus the OS being previously installed on a partition and needing to create restore discs?

Yes, you'll end up with the same as you would get on a store-bought system (but without extra guff that would usually be loaded on brand-name systems). As you note, you'll have the install disk rather than say a restore partition.

With a store bought system, the manufacturer/supplier would be supposed to help you if you had problems with the OS, eg if some drivers had conflicts or something. If you set up OEM Windows yourself, you'll have to work out any problems by yourself, since you have become the system builder. But of course there are folk here able and willing to help.