I'm struggling here. Just spent the weekend familiarizing myself with Linux and getting Slack 9.0 installed. Upon my very 1st HD boot, GRUB v. 1.5 begins loading and immediately ceases, displaying the rather uninformative "Error 15"

HD configuration is as follows: Two IDE drives. Slave is FAT32 with a bunch of data files. Master is partitioned into hda1(Linux swap) and hda2(filesystem). I really thought I had the install procedures down. Everything went smoothly and now this!

So what does Error 15 mean, anway? Google tells me something about "missing files."

Another oddity, why is GRUB trying to boot my system in the first place? I had been under the impression that LILO was slackware's bootloader of choice. Indeed, I configured it during the install!

Does the answer lie in the MBR. Should I have told LILO to take residence there during the install, rather than in the "super user blocks" (?)

I haven't a clue on this one. I don't have a floppy, so the only way I can even get past the two lines that GRUB gives me during a HD boot is to re-insert the slackware installation CD.

Any help on this matter will be greatly appreciated.

Did you have any other distro installed on this machine previously? That's all can think of.
I do think the MBR is your problem. I also think it can be resolved by installing lilo to the MBR. You should run "liloconfig" as root. That gives you an easy way of reinstalling lilo. You didn't mention any thing about other OS's so configuring shouldn't be difficult.

Thanks for the info. I'll try tinkering around with liloconfig. As you note, the only OS I want on this machine is slack linux, so I don't have to worry about dual boots, making room for m$ etc.

I DID have a version of Ark Linux installed prior to slack, but I thought when I formatted the drive (full) and installed slack that MBR would be overwritten. Evidently this is not the case?

Any tips on what I should be looking for in liloconfig? I recall it being pretty large

You're right, if you don't install lilo to the MBR, it will most likely not be overwritten. As for liloconfig, in the main menu select "expert".
In the next menu select "begin" and follow the on-screen instructions" next, select "Linux" and, again, follow the instructions. Next select "Install" and that's it. Be sure to select MBR when asked for the location!

Liloconfig did the trick. Slack is officially up and running. I'm in business!

Thanks again for the tips! I thought I was losing my mind for a while there.

Yay! Another happy Slacker!