Programming won't probably help you too far with installing Slackware, I'm afraid
Well, Slackware indeed prefers to use LILO as the bootloader. There is GRUB available too, but it won't let you install it in the semi-guided setup; if you want to have it instead of LILO, you need to install it yourself. Either after the setup before you reboot (leaving LILO out completely), or after booting (with LILO) to your new Slackware, and doing it from there.
I've had so much trouble with LILO that I've given up using it a long time ago. Grub is a lot easier to maintain once installed, and I'm waiting even more from the new version of it once it's released (if it is).
Well, your trouble is not the system installation if it went trough smoothly, but bootloader. So head on and search for "how do I reinstall bootloader (Grub)?" Basically boot from a bootdisk or Slackware CD, mount local partitions, enter chroot environment and then just install Grub.
I'd be curious to know why exactly LILO fails to install. I'm not really surprised, but curious. Most often I was able to install it fine during Slackware setup, but making changes to LILO config, followed by re-installing it to MBR always failed - it appeared that only Slackware setup was able to put LILO into MBR for me
nice. Well, Grub does a lot better, so I won't complain.
So: search LQ for grub installation instructions (or Grub website, or some site), boot from your Slackware setup disc, don't enter the setup program, but instead 'mount' your local partitions, 'chroot' and so on. Once the bootloader is reinstalled (Grub, if you prefer), reboot and see if it helped. It's your own decicion which bootloader you use, but if you want to have less trouble, I'd say pick up Grub, and don't overwrite it unless you have to.