So I'm at a loss. I've read through the posts, tried a couple things suggested...and now nothing boots.
I've got a homebrew desktop, not a Dell or Compaq or any of that. Dunno what the motherboard is, but here's some of the specs:
Pentium III, 866 MHz
Pri. Master Disk: LBA, ATA 33, 46116MB
Pri. Slave Disk: none

It's got two IBM hard drive's in it...one slaved to the other, which is odd it says none above. I've used the slave drive in windows without any issues...the jumpers are set to slave, not cable select. Anyhow, I recently wiped the primary drive of my windows 2000 installation in exchange for a full install of windows xp. Things were working fine and I slapped in an old hard drive specifically to dual boot linux. Was accessing the second hard drive just peachy in windows, then I tried to put fedora core 5 on it. During installation, I selected to put grub on MBR, but it did install a boot directory on the second hard drive as well. I also selected it to load Other (which I labeled windows) by default. To begin with it simply booted up into windows like grub didn't exist, so I hit the forums and found the suggestion to try:
grub-install --recheck /dev/hda
The command itself was successful, however this simply made things worse...now my computer will not boot at all.
I then tries entering into grub itself and typing:
root (hd1,0)
setup (hd0)
quit

It attempts to load into grub, at which point I receive grub error 21.
I've not swapped anything around, nor messed with my MBR since this has happened.
Anyhow, my grub.conf is as follows: (tho is it even using it, if it's got a boot directoy on the secondary hard drive?)

#boot=/dev/hda
default=1
timeout=10
splashimage=(hd1,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora Core 5 (2.6.15-1.2054_FC5)
root (hd1,0)
kernel /vmlinuz-2.6.15-1.2054_FC5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.15-1.2054_FC5.img

title Windows
rootnoverify (hd0,0)
chainloader +1

I think I've just got something pointing to the wrong spot, but I don't know how to find out what or how to fix this. Please help...my computer is a big hunk of metal at the moment, and I don't want to touch anything more for fear of messing it up even farther.

First, let's look at the grub error;

21 : Selected disk does not exist
This error is returned if the device part of a device- or full file name refers to a disk or BIOS device that is not present or not recognized by the BIOS in the system.

Now, from your post;

"Pri. Master Disk: LBA, ATA 33, 46116MB
Pri. Slave Disk: none

It's got two IBM hard drive's in it...one slaved to the other, which is odd it says none above."

If this is what the bios reports, then the bios is not seeing the second drive.

Without knowing what motherboard that you have, so we can know what bios is in the system, you will have to proceed accordingly.

If the drive was seen by the bios before installing Fedora, then the older bios that you have is not seeing the secondary drive because either;

1. The drive went south, or;

2. The geometry of the drive is not being seen correctly by the older bios in your system, with the linux partitions on it.

Try getting into the bios and setting the drive from "auto" detect to "LBA" mode. this changes how the bios sees the geometry of the drive. Older bios' have issues with this and changing to LBA mode usually solves this problem.

Then see if the drive is seen by the bios.

It would be nice to know the model number of the affected drive. What size hard drive is it?

"Was accessing the second hard drive just peachy in windows, then I tried to put fedora core 5 on it. During installation, I selected to put grub on MBR, but it did install a boot directory on the second hard drive as well. I also selected it to load Other (which I labeled windows) by default. To begin with it simply booted up into windows like grub didn't exist"

In a default Fedora installation on a second hard drive, Fedora assumes that that is the only drive in the system, unless you pick the advanced partition option when formatting the drive during the installation.

A boot directory on the drive is always made, which houses the vmlinux, initrd, config file, grub reference files and system.map file.

If you choose to install the actual booloader to the second drive (which is by default in your case when you installed Fedora), the MBR is written to the second drive.

Hence, this is why you booted right into Windows. The MBR of the actual boot drive (primary master) still had the bootloader for Windows only.

Now, this is where things get cloudy. You boot into rescue mode.

Did you make sure that the sysimage was loaded? in Fedora Core 5, during the recue boot, Fedora tries to see the installation and mount the sysimage. You get a message asking if you want to do this, or skip the detection. If there is something wrong, the image is not mounted and you should have received a message that not all the files were loaded.

If you choose the skip this step, then you need to mount the sysimage manually.

Then you can do the grub-install --recheck /dev/hda

Same applies to running;

"I then tries entering into grub itself and typing:
root (hd1,0)
setup (hd0)
quit "

Then to respond to your other question;

"Anyhow, my grub.conf is as follows: (tho is it even using it, if it's got a boot directoy on the secondary hard drive?) "

Two differnt issues, as described above. There is a /boot partition, with the reference files described above in it. The MBR is installed wherever you put it, with the actual bootloader.

Danlef for president!
Somehow my bio had indeed stopped seeing the secondary drive. Very strange. Anyhow, setting it to LBA has fixed the problem right quick. So glad I listened to danlef in the previous posts not to touch anything, mess with the mbr, swap out hard drives, etc. Quick and easy...you rock danlef!

Well I can't vote for a guy for president without spelling his name right...
DANLEFF FOR PRESIDENT!