Are web sites like softwarecb.com legal?  They are even advertising on
google.  I just bought a copy of Illustrator CS on there but I could
not register it on Adobe's site as I got a message saying that copy
has already been registered.  The company says that the copy is legal
but I could not register it as it is for archiving purposes.  What is
that supposed to mean?

What they are saying is that under 17 U.S.C. Section 117 they are
permitted and make and sell to you an archival back-up copy of the
software.  So under their theory, they buy one original copy of the
software.  Then they make an archival or back-up copy and sell it to
you--that's why you get no media or manuals--they just copy the CD and
permit you to download it.  In their view, the copy they make is the
permitted archival copy and they are selling it to you under Section
117(b).

The problem is that 117(b) says that you can sell the archival copy
"only along with the copy from which such copies were prepared, only
as part of the lease, sale, or other transfer of all rights in the
program."  In other words, to fall under Section 117, softwarecb.com
would need to give you both the archival back-up copy AND the original
version along with all media and manuals.  As it stands, this looks
like pure piracy to me.  Adobe apparently agrees since you could not
register your copy--softwarecb.com has apparently already registered
their original copy.

Helpful reading can be found at http://www.bsa.org/usa/antipiracy/ and
http://www.siia.net/piracy/.