This question rests on the following two things being true (so the
researcher should verify or discredit them first): (1) copying music
from my legally-purchased CDs to my computer or Ipod for personal use
is not illegal (i.e., does not violate copyright law); (2) copying my
legally-purchased VHS movies to DVD is illegal (i.e., violates
copyright law). My question is this: What?s distinguishes these two
situations that justifies and explains why the law would be different?
They would seem to me to be identical in terms of how they should be
treated under copyright law. In both cases, I?m converting ?content?
from one storage form to another. In both cases, the existing form
cannot be considered obsolete (and, in any case, VHS tapes seem much
more obsolete than CDs). While I obviously see the movie industry?s
desire to force people to re-buy their entire VHS movie collections on
DVD rather than converting them (resulting in billions of dollars of
profit), the music industry would have this same incentive to legally
prevent purchasers of CDs from copying their music to other
technologies and instead require them to re-buy the music (e.g.,
through downloads). Yet this latter situation seems absurd (i.e.,
people with a 1000 or more CDs are NOT going to buy that same music
through internet downloads). I?m aware that people largely DID
repurchase their music collections when LPs gave way to CDs, but would
it have been illegal for them to have copied their LPs to CD? Also, in
the music situation, people routinely copy CDs to tape, with no
copyright violation (to my knowledge). Is this just a situation of the
movie industry being more powerful than the music industry? I?m
baffled!

What makes you think it's illegal.  It would seem to fall under fair
use, regardless of claims made by the movie industry.

1) copying music from CDs to Ipod or other device, legal.
2) copying a non-macrovision VHS to DVD or other device, legal.
3) copying an unencrypted DVD to VHS or other device, legal.
4) copying an encrypted DVD to VHS or other device, technicly legal
but imposible to do legally.

Items 1 to 3 are legal because of the 'fair use' principle. It allows
you, among other things, to make personal backups of copyrighted works
you legally obtained without infringing on copyright. This is also
known as format shifting and while the content industries would love
to force you to buy your collection again on new media, anything they
say on this subject is FUD.

The problem comes with item 4. The DMCA makes it illegal to defeat a
"technological measure that effectively controls access to a work".
The .vob (video) files on most commercial DVDs are encrypted with CSS
(Contant Scrambling System). This is what prevents you from just
putting the DVD in your computer and reading the files with windows
media player.

You are allowed to make a copy of a DVD, but it will not work. The
reason is that your copy will also be encrypted but it will not
include the decryption key. This takes some explanition.

Whenever you encrypt something, you need a way to decrypt it in order
to let the customer view it. With a DVD, the key is on the disk. It is
located in a certian physical spot on the disk. All blank DVD come
from the factories with that certian spot on the disk ruined so no
data can be writen thier. This means that you can not copy the key and
the DVD player has no way of decrypting the disk. Thus the only way to
make a WORKING copy of a DVD is to decrypt the .vob files, than burn
the result to a blank disk. Your copy will not be protected and will
not need to write anything to the ruined key area. When you decrypt
the DVD you are violating the DMCA.

More manufactures are moving to copy protect all the new content they
relese so it will fall under the protection of the DMCA, thus doing an
end-run around fair use. The only reason items 1 to 3 are still legal
is because the contant on a CD is not encrypted.

I would suggest checking out the DMCA page of the EFF.
http://www.eff.org/IP/DMCA/

It seems to me a reasonable answer still hasn't been posted. The
detailed answer reguarding coping DVD's to other media was, however
that's not the question here.

It seems to me that fair use should apply.  The mention of a key not
being present on a CDA (audio CD) may be fact, however is not CDA a
licensed media that is not analog and requires licensed digital media
device to decipher what all the dips and dashes mean?  And recording
this media to a tape uses the licensed media device to make a "FAIR
USE" Back-up not incorprating the required decipher media it was
original sold for. (DVD to VHS)

Now for the macrovision part.  You purchase a VHS tape and on the tape
(every original i own) is the FBI copy warning. That very same warning
implies that "FAIR USE" laws apply.  That is the contract we accepted
when we bought the Tape and that the contract that is still ineffect. 
If new media comes out that we are able to duplicate (back-up" our
purchased media to, the fair use law still applies.  By passing
Macrovision is not something that requires any non standard or altered
signel.  Older VCR's don't support the macrovision code and don't pass
this information to the TV or to any other Media playing/recording
devices. Therefor you did no illegal circumvention of copy protection
to make a DVD recording of your VHS originals.