Re: "would it be possible to get a 5.25 to work in say an older laptop w/an
integral 3.5?"
Maybe.
Quite a few Toshiba laptops have an external floppy drive port. It is a
true floppy port, designed to interface to a 34-pin floppy interface. Two
different connectors were used, the "standard" Toshiba floppy port connector
used in every model computer except the Tecra 8000, and a slightly different
connector used in the Tecra 8000 series.
These connectors are found in the Satellite 400 series laptops (two
distinctly different sets of laptops, the "early" 400 series (400 to 435,
Pentium I's) and the "late" 400 series, 440 to 490, Pentium MMX and even a
Pentium II). They are also found in the Tecra 8000 (different connector),
which used both Pentium II and Pentium III CPU (266MHz to about 500MHz). I
think that there are other Toshiba laptops that have a similar connector as
well, in the Tecra and Portege line (and also the libretto models).
Note, since this port was used for the 3.5" floppy drive, you generally
won't be able to have both 3.5" and 5.25" drives installed at the same time
(but, on some of these, the very reason for the port was that there was an
internal drive bay that could either contain the floppy drive internally, or
a CD-ROM drive. Not sure if you could use an internal and an external
floppy concurrently in those models).
Also, Toshiba assumed that the external drive was 3.5" and there is no
provision in the BIOS to configure the bios and software for any other
floppy drive format.
Finally, the hardware reconfiguration (cable) will be a bitch to figure out,
although it is conceptually possible. While the external floppy has the
34-pin electrical interface, mechanically it's not a standard 34-pin IDC
connector, it's a flat "flex cable", and reworking the cable to connect to
a
34-pin standard interface will take some effort.
The good news is that you can buy entire laptops in this series for as
little as $15, and you can find the external floppy caddies for $5 (source
of the cable and connector that mates with the laptop).