Quote Originally Posted by foamrotreturns
OK i think i'm getting the hang of this...
I'm going to run the ISO from an ext3 filesystem. it's located at /isos/whoppix on my (hd0,1) as well as the minirt26.gz and linux26 files. so here's what i've got in my menu.lst file for that entry:

title WHoppix Linux
root (hd0,1)
kernel /isos/whoppix/linux26
initrd /isos/whoppix/minirt26.gz

Is that all I need? i'd like to prevent writing to the HD at all costs - is there something I should be appending to the root line to make it mount the FS read only?
Yes, pretty close to that:
You need to add some "cheatcodes" after the kernel options and you probably want to use my minirt26_ntfs.gz even though you are not using the ntfs driver, because of the "bootfrom" cheatcode (required to boot from the iso file) which is not handled properly by the linuxrc file in the regular minirt26.gz.
So to summarize I will suggest something like this for your menu.lst:

title Whoppix 2.6-sp1 kernel 2.6 from hda2 ISO file
kernel (hd0,1)/isos/whoppix/linux26 ramdisk_size=100000 init=/etc/init lang=us apm=power-off nomce bootfrom=/dev/hda2/isos/whoppix/*.iso quiet noprompt (all on a signle line from the kernel ...)
initrd (hd0,0)/isos/whoppix/minirt26_ntfs.gz
boot

And as far as I remember, all partitions are read only by default and it is actually not that obvious to grant write access to the boot partition, where the kernel, initrd and iso file are located.
Cheers, Gilles