Boot loader: Grub
I dualboot 1 Redhat 9.0 and 1 windows xp pro in one hard disk in different partitions. When computer boots up, it goes to a screen that appears 3 options (not 2, I set up windows xp first and then Linux Redhat, each OS I spent only one time). If I choose the first or second option, the computer boots into the same way, Red Hat. I notice the difference between two of them is "one has the word smp but the other is not"

This is my original "grub.conf" file
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You do not have a /boot partition. This means that
# all kernel and initrd paths are relative to /, eg.
# root (hd0,2)
# kernel /boot/vmlinuz-version ro root=/dev/hda3
# initrd /boot/initrd-version.img
#boot=/dev/hda
default=0
timeout=10
splashimage=(hd0,2)/boot/grub/splash.xpm.gz
title Red Hat Linux (2.4.20-8smp)
root (hd0,2)
kernel /boot/vmlinuz-2.4.20-8smp ro root=LABEL=LINUX hdc=ide-scsi
initrd /boot/initrd-2.4.20-8smp.img
title Red Hat Linux-up (2.4.20-8)
root (hd0,2)
kernel /boot/vmlinuz-2.4.20-8 ro root=LABEL=LINUX hdc=ide-scsi
initrd /boot/initrd-2.4.20-8.img
title Windows XP professional
rootnoverify (hd0,0)
chainloader +1

Do I need to delete one of two options that boots into redhat 9.0? Is it dulicate option? If not, What's the difference between option 1 and 2?

As I can see these are not duplicate options though they seem to be booting similar kernels. vmlinuz-2.4.20-8xxx is the name of your kernel. Do both work? And this grub.conf was generated by anaconda at installation? If both work, choose the one that works better. If they work the same, choose the one you prefer. Then go to /boot and delete vmlinuz-2.4.20-8xxx (the one you did not choose) and System.map2.4.20-8xxx(the one you did not choose) and initrd-2.4.20-8xxx (the one you did not choose). If you delete any symlinks reconnect them to fit your option. After that edit grub.conf file and delete the lines of the option you did not choose. reboot and you should be off with two options and only one kernel.

“smp” kernels are for multiprocessor systems, but will usually run on single processor systems. If you have one CPU, then you don’t need the smp kernel.