Well, I don't quite see the need for both Redhat and Slackware
myself, but if you want to do that you'll probably want two small
partitions, /boot1 and /boot2, towards the beginning of the disk, your
Windows partition, then the rest of your Linux partitions. That should
allow you to use loadlin unfettered.
> How much space will each OS take up?
Windows should be very happy with ~1 GB or more; both Linuxes
together should be happy ~1 GB or more.
> Can I usefully share some directories (Netscape, say) between Linux
> distributions, or should I plan to install and configure even large
> applications twice?
Yeah. The main issue would be installing glibc under slackware (or
using RedHat's glibc) so that you could use glibc binaries. Again, I don't
see much point to putting two distributions on your system. I mean,
putting Debian on one parition just to see what the default setup looks
then reclaiming would be one thing, but there's wouldn't be much reason to
keep it. With enough effort, you can make any distribution identical to
any other distribution.
> Should I install Windows first? Last? Which FDISK should I use to
> carve up the space?
These are answered in the HOWTOs, but... Windows first, Linux
next. As for partitioning strategies, the general recommendation is to use
the operating system's fdisk to carve up that space, but my perception is
that LInux fdisk would probably be better.
> I'd like to boot from LILO, if possible, and avoid LOADLIN.
Yeah - putting /boot (or a smallish /, for that matter) at the
beginning of your hard drive should do the trick.