1) The goverment of the US produces hundreds of manuals every year. 
Some are hard copy and some are electronic.  Are these copyrighted?
1a) I saw somebody selling CD-ROMs online and I knew they were just
selling a compilation CD of these manuals.  Is this legal?

2) I used to run a computer store.  We sold people a CD-ROM for $4.99
that had all the drivers for their computer on it (which we downloaded
from the internet).  Was that legal or are there patents on regular
drivers?

3) If a company owns a copyright on a movie and they go out of
business, is the copyright still good?  If so, how long is it good
for?

You may want to consider posting these three questions separately.
Multi-part questions sometimes go unanswered because a Researcher is
not able to find information to answer all of the parts. Since we know
in advance that we won't be paid unless we can successfully perform
three separate research projects, we may be disinclined even to try.

If this were three questions, I think you'd stand a better chance of
getting a good response.

Your questions lack the specificity to be answered exactly. 
Compilations of government documents is generally ok if they are
indeed a part of the public domain.  Inside the cover it well tell
you.  I could not tell if the $4.99 cd was drivers that were public
domain or not.  There could have been a problem if someone owned the
rights and your cd was a bootleg.  As for a copyright, it ius most
likely that an intangible such as a copyright would not just go away
because a company went out of business.  I am sure that there would be
either a successor in interest or a creditor that would come before a
claimant who was not connected in any way.