I have 2 hard drives but linux only sees one at the lilo prompt. Is there something I need to modify in lilo for it to see the other drive?
I would like to have slackware on 2 different hard drives like having 2 different systems.

# LILO configuration file
# generated by 'liloconfig'
#
# Start LILO global section
boot = /dev/hda
message = /boot/boot_message.txt
prompt
timeout = 10
# Override dangerous defaults that rewrite the partition table:
change-rules
reset
# VESA framebuffer console @ 1024x768x256
vga = 773
# Normal VGA console
# vga = normal
# VESA framebuffer console @ 1024x768x64k
# vga=791
# VESA framebuffer console @ 1024x768x32k
# vga=790
# VESA framebuffer console @ 1024x768x256
# vga=773
# VESA framebuffer console @ 800x600x64k
# vga=788
# VESA framebuffer console @ 800x600x32k
# vga=787
# VESA framebuffer console @ 800x600x256
# vga=771
# VESA framebuffer console @ 640x480x64k
# vga=785
# VESA framebuffer console @ 640x480x32k
# vga=784
# VESA framebuffer console @ 640x480x256
# vga=769
# End LILO global section
# Linux bootable partition config begins
#image = /boot/vmlinuz
# root = /dev/hda1
# initrd = /boot/initrd.gz
# label = Linux
# read-only

image = /boot/vmlinuz-ide-2.4.32
root = /dev/hda1
label = linux24
read-only

image = /boot/vmlinuz
root = /dev/hda1
label = 2.6
read-only

# Linux bootable partition config ends

bash-3.1$

Make an entry for the slackware entry in the other dirve in your /etc/lilio.conf e.g.

What do you mean? Put that code in place of something in /etc/lilo.conf?

What I need to do is install Linux on a empty HD that is already installed and take this one out to send in for replacement then reinstall it with another slack install so I can choose either one from lilo and have 2 separater hard drives.

Should I unplug this hard drive and install Linux on the existing blank drive? If I do that then how do I get the second (blank) hard drive up and running when i reinstall it?

My advice above is exactly what you need. Install Slack on the hard drive you have right now. When you get your other drive back, just plug it back in as a slave drive and then install the version of Slack that you want on this drive. After that edit the /etc/lilo.conf of your main Slack installation (the one on your first hard drive) and add an entry for the Slack on the second hard drive using the example code I posted above.

But, How do I install slack on the other blank drive now, so I can get it up and running before I take this one out?
Does it matter if both drives are named hda1 in lilo?

Thanks.