After installing Fedora 7, and reboot, I got error of "Operating system not found".
the grub.conf is

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
# initrd /initrd-version.img
#boot=/dev/sdb
default=2
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.20-2925.9.fc7xen)
root (hd0,0)
kernel /xen.gz-2.6.20-2925.9.fc7
module /vmlinuz-2.6.20-2925.9.fc7xen ro root=/dev/VolGroup00/LogVol00 rhgb quiet
module /initrd-2.6.20-2925.9.fc7xen.img
title Fedora-base (2.6.21-1.3194.fc7)
root (hd0,0)
kernel /vmlinuz-2.6.21-1.3194.fc7 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
initrd /initrd-2.6.21-1.3194.fc7.img
title Other
rootnoverify (hd1,0)
chainloader +1

device.map was..

# this device map was generated by anaconda
(hd1) /dev/sda
(hd0) /dev/sdb

(Please don't doubt me of asking hd1 or hd0 was wrong.. It is right and 100% sure..) By the way, /dev/sdb is 1TB usb drive. /dev/sda was xp hard disk

file of /etc/fstab

/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/VolGroup00/LogVol01 swap swap defaults 0 0


And hard disk configuration
/dev/sda1 (XP)
/dev/sdb1 (/boot)
/dev/sdb2 (LVM, ext3 main)

This is fdisk -l

Disk /dev/sda: 52.1 GB, 52108145664 bytes
255 heads, 63 sectors/track, 6335 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 5702 45801283+ 7 HPFS/NTFS
/dev/sda2 5703 6335 5084572+ 77 Unknown

Disk /dev/sdb: 1000.2 GB, 1000207286272 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 * 1 13 104391 83 Linux
/dev/sdb2 14 121601 976655610 8e Linux LVM

I currently have two active partition: one /dev/sda1 and one in /dev/sdb1.
Thanks.

During the Fedora install, where did you tell it to put the bootloader?

From your description, I can't tell if you ever see a GRUB menu--or does it go directly to the "Operating system not found" message.

I assume that all the configuration information is gathered by running with the live CD....That COULD account for what appears to be an anomaly--ie, one would normally expect sda to hd0 in "grub-speak"

Try this:
(Running from the live CD)
use fdisk to turn off the bootable flag on the Linux /boot partition.
enter "grub" to start the GRUB shell
root (hd0,0)
OR
root (hd1,0) One of these will show up as a Windows partition and the other one will show as Linux
After entering the root command which shows the Linux partition, then put in blank floppy and enter:
setup (fd0)
Now you can boot from the floppy
If you now get a GRUB menu, then we know that GRUB never got installed to the MBR (at least on the right drive)

If you can get this far, then we can get you to the last step of setting up the grub config file

(see the link below also)

I told Fedora installer to install my bootloader in /dev/sdb.
When the option came about installing bootloader, there was only one option which was to install to /dev/sda. However, I checked "Configure the GRUB (Or whatever)" and switched the hard disk confinguration (Making grub to install to /dev/sdb). Also, I switched BIOS settings before installing. OK, I will try your suggestion... But, since I don't have floppy drive availble, can I load to CD?

I didn't see the GRUB menu., too.

Right--you did not see the GRUB menu because you but GRUB on sdb, and the BIOS never found it.

You can put grub on the mbr of sda--as long as you have a Windows CD** to recover the mbr if their are any issues. You can also put grub on sda3 and then make an image of it to put on the Windows drive. Search here on "dual-boot using NTLDR" (I've never done it)

**If you do NOT have Windows CD, you can always backup the Windows MBR code from your live CD. BUT--I personally would be reluctant to keep tweaking this system if I had no way of recovering Windows.

Let us know which path you want to follow and which details need more elaboration.

I don't have Windows Recovery CD... OK, so I just can install GRUB on partition.. OK, first I will give a try to install to /dev/sdb's MBR and then to /dev/sda4's MBR.
If it fails, I will post the problem again. Thanks, Pixellany!