There are two valid and conflicting points here. The first is
legal: I (not being a lawyer or anything) believe it is probably
legal to take data from any system you legally acquire. The
I am not even convinced of that. If I get a computer with commercial
software on the hard disk, and you keep the original master disks, I
don't think I am allowed to run said software. In fact, it's not clear if
you are in violation of the license (you've transfered a copy), if I am
(I am using a copy without a valid license) or we both are.
Old software is the lifeblood of old computers. Until I get some sort of
official cease and desist order I will generally put whatever I can find on
any old system I put together for a person. The end user is welcome to
delete etc. as their own conscience dictates.
When I get an old system in, and the hard drive is full of "stuff", most of
the time I back it up to a 640 MB network server partition, which gets
dumped to CDR when it fills up. My goal there is to perserve unique
software, and to harvest software serial numbers if needed. My opinion is
that the "license" belongs to whoever squeals the loudest with a valid
serial number. Just having the software on a hard drive makes my case weak,
but if no one else makes a better claim, ie has a set of floppies for that
serial number, then I think it is good enough.