One way (there are many) to add a kernel to the installation disc.
Download from you favorite mirror these complete directories -
isolinux/
kernel/
Place your custom kernel inside kernel/ so you'll now have
kernel/
-------huge.s/System.map.gz bzImage config
-------speakup.s/System.map.gz bzImage config speakup_decpc.ko
-------yourkernl/System.map.gz bzImage config
You'll then have to edit isolinux.cfg to add the correct lines for your additional kernel.
Code:
label huge.s
kernel /kernels/huge.s/bzImage
append initrd=initrd.img load_ramdisk=1 prompt_ramdisk=0 rw SLACK_KERNEL=huge.s
label speakup.s
kernel /kernels/speakup.s/bzImage
append initrd=initrd.img load_ramdisk=1 prompt_ramdisk=0 rw SLACK_KERNEL=speakup.s
label yourkernl
kernel /kernels/yourkernl/bzImage
append initrd=initrd.img load_ramdisk=1 prompt_ramdisk=0 rw SLACK_KERNEL=yourkernl
Create the slackware/ directory to mirror the package sets if you do not plan on doing a network install. To make the iso image, follow the instructions in isolinux/README.TXT.
mkisofs is available for Windows. If you wanted to edit an already downloaded iso image inside Windows, you can use a disc mounting utility (MagicDisc for example), I'd personally start with the bare directories and just burn isolinux/ kernels/ and an empty slackware/ to disc to make sure things work first.
But, all of the above may not be neccessary if you give some details to the error message your are getting, and a little insight to the hardware you're running. Motherboard model/maker, chipset model,maker ..
The huge.s kernel has 99.9% of the possible hardware modules built in. You may simply need to pass a couple of options on the boot prompt for not loading conflicting drivers, or to bypass a buggy BIOS.