Alot of my friends have dell 4550's and all tried putting fedora on them. After Instalation, when they reboot, All it does is say GRUB in white text on a black screen. NOTHING ELSE HAPPENS! This also happens on my computer. What is wront, and how to I fix it?

When you hit return at GRUB, does it prompt GRUB again? If yes, type the following
(you can use the TAB key to autofill or give you more options)
root (hd<hit tab and select the appropriate number>,<tab to select the boot partition>
kernel /boot/vmlinuz root=/dev/hdxn (where x is the drive and n is the partition where / resides)
initrd /boot/<hit tab> to select the appropriate image file (ending in img)
boot
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Method 2
You may try this

boot from your installation CD
at the boot: prompt, type linux rescue
Follow the instructions -- You will be instructed that the rescued partitions are at /mnt/sysimage
At the initial hash (#) prompt, type chroot /mnt/sysimage
at this hash (#) prompt, type grub-install /dev/hdx where x is the drive that has the MBR.