I have 2 hard drives, the first with Windows XP and the second with fedora core 2. I installed Grub onto the mbr of the windows drive and everything works fine. What doesn't work is when I try to add extra hard drives. This causes Grub to stop after displaying the string "GRUB" but before displaying "loading stage2." I tried re-installing fedora/Grub with the hard drives in, but the same thing happens unless i remove the extra hard drives. Any ideas would be appreciated.

Post how the drives are configured i.e. master / slave before and after you add the drives.

I would say that when you add the drives the drive with linux is no longer where grub thinks it should be. It is based on how the drives are recognized by the BIOS.

The windows drive is SATA and is set to the first boot device in BIOS. The linux drive is the secondary master (IDE) and is set to the second boot device. the two additional drives are on primary master/primary slave, with boot order 3 and 4. The order of the first two devices does not change, and grub is read from the MBR of the windows drive, but the OS select menu is never reached. Also, when grub is installed with all the hard drives preasent, the error still occurs, so I would think that it would be able to locate the drive. Not sure though.

grub is a 2 stage boot loader and needs to know the location of the linux drive. grub will use the BIOS to determine recognized drives and any drives on the primary controller will be found first. So grub will try to find the 2nd stage on the primary master instead of the secondary master.

Now did you reinstall the OS or just grub when the extra hard drives were present? If you just reinstalled grub without making any changes to menu.lst file you would still have the same problems.

You can boot using the install CD select rescue mode. The root partition will be mounted at /mnt/sysimage. Now type in the command:
chroot /mnt/sysimage
Edit the /etc/grub.conf file using the vi editor
vi /etc/grub.conf

Look at line that says root(hdx,y)
The first recognized dirve is 0, next is 1 and so on. I assume that this line is root (hd1,0). With the extra drives installed it is now
root (hd3,0). Basically just add 2 to the x value.

In using vi press the Insert key. use the arrows to navigate to the lines, delete then type in the new values.

To save the file press the escape key to exit insert mode then press the keys
:wq

To exit vi without saving the command is:
:q!