OEM in most cases is looked at as an upgrade to an
existing system therefore programs, cables etc are
not needed nor are they wanted by those of us who
purchase oem.
You pay top dollar for retail packages when in most
cases you dont want or need half the software titles
that ship with the product but you still PAY for them.
You definately need to look at EACH oem offering to
determine if it comes with everything you need and
even the warrantys differ from oem to oem.
The manufacturer looks at the oem pc market as
generally the more experienced market and can offer
better warrantys because of the experience whereas
the retail market is more likely to have less experience
and more likely to have problems with the purchase and
therefore the warranty might be of a shorter period of
time.
The warranty is not a factor of the likelyhood of part failure
but of having to offer support for the most rudimentary
of installation or use questions the a more experienced
user would have no need of.