I tried to triple boot Windows xp, Fedora 14 and Ubuntu 10.04. I first installed Windows xp, then fedora followed by Ubuntu.

The problem is that i don't get option to boot Ubuntu while Xp boots fine. It seems Ubuntu was unable to replace Fedora's grub with its own at MBR. Looking at their grub conf file, Fedora and Ubuntu identifies same harddisk as two different devices and i do have another 80 GB harddisk which doesn't have any OS.

Below is the details on my partitions and partial information from grub files of both OS.

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *          63    40965749    20482843+   7  HPFS/NTFS
/dev/sda2       102414436   312576704   105081134+   f  W95 Ext'd (LBA)
/dev/sda3        40965750   102414374    30724312+  83  Linux - /Home (for fedora)
/dev/sda5       102414438   204812684    51199123+   7  HPFS/NTFS
/dev/sda6       204812748   253634219    24410736   83  Linux -- ubuntu
/dev/sda7       253634283   302455754    24410736   83  Linux -- fedora
/dev/sda8       302455818   312576704     5060443+  82  Linux swap / Solaris

grub.cfg from ubuntu

### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu, with Linux 2.6.32-21-generic' --class ubuntu --class gnu-linux --class gnu --class os {
    recordfail
    insmod ext2
    set root='(hd1,7)'
    search --no-floppy --fs-uuid --set cd55e078-a2c1-4d8a-9e87-ae838b6f4a05
    linux   /boot/vmlinuz-2.6.32-21-generic root=UUID=cd55e078-a2c1-4d8a-9e87-ae838b6f4a05 ro   quiet splash
    initrd  /boot/initrd.img-2.6.32-21-generic
}
menuentry 'Ubuntu, with Linux 2.6.32-21-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
    recordfail
    insmod ext2
    set root='(hd1,7)'
    search --no-floppy --fs-uuid --set cd55e078-a2c1-4d8a-9e87-ae838b6f4a05
    echo    'Loading Linux 2.6.32-21-generic ...'
    linux   /boot/vmlinuz-2.6.32-21-generic root=UUID=cd55e078-a2c1-4d8a-9e87-ae838b6f4a05 ro single 
    echo    'Loading initial ramdisk ...'
    initrd  /boot/initrd.img-2.6.32-21-generic
}
### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
    insmod ext2
    set root='(hd1,7)'
    search --no-floppy --fs-uuid --set cd55e078-a2c1-4d8a-9e87-ae838b6f4a05
    linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
    insmod ext2
    set root='(hd1,7)'
    search --no-floppy --fs-uuid --set cd55e078-a2c1-4d8a-9e87-ae838b6f4a05
    linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Microsoft Windows XP Professional (on /dev/sdb1)" {
    insmod ntfs
    set root='(hd1,1)'
    search --no-floppy --fs-uuid --set cad48cc6d48cb5eb
    drivemap -s (hd0) ${root}
    chainloader +1
}
menuentry "Fedora (2.6.35.14-96.fc14.i686) (on /dev/sdb6)" {
    insmod ext2
    set root='(hd1,6)'
    search --no-floppy --fs-uuid --set 6aee34cf-f77a-489a-9361-85d07194b84b
    linux /boot/vmlinuz-2.6.35.14-96.fc14.i686 ro root=UUID=6aee34cf-f77a-489a-9361-85d07194b84b rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
    initrd /boot/initramfs-2.6.35.14-96.fc14.i686.img
}
menuentry "Fedora (2.6.35.6-45.fc14.i686) (on /dev/sdb6)" {
    insmod ext2
    set root='(hd1,6)'
    search --no-floppy --fs-uuid --set 6aee34cf-f77a-489a-9361-85d07194b84b
    linux /boot/vmlinuz-2.6.35.6-45.fc14.i686 ro root=UUID=6aee34cf-f77a-489a-9361-85d07194b84b rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
    initrd /boot/initramfs-2.6.35.6-45.fc14.i686.img
}
### END /etc/grub.d/30_os-prober ### 

grub.conf from fedora

 default=0
timeout=5
splashimage=(hd0,5)/boot/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.35.14-96.fc14.i686)
    root (hd0,5)
    kernel /boot/vmlinuz-2.6.35.14-96.fc14.i686 ro root=UUID=6aee34cf-f77a-489a-9361-85d07194b84b rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
    initrd /boot/initramfs-2.6.35.14-96.fc14.i686.img
title Fedora (2.6.35.6-45.fc14.i686)
    root (hd0,5)
    kernel /boot/vmlinuz-2.6.35.6-45.fc14.i686 ro root=UUID=6aee34cf-f77a-489a-9361-85d07194b84b rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
    initrd /boot/initramfs-2.6.35.6-45.fc14.i686.img
title Other
    rootnoverify (hd0,0)
    chainloader +1