Make sure your HDD with Grub is selected as the first boot device in grub menu. Bios flashing might have set your setting to default.
If that is not the issue and still can't see Grub, boot an Ubuntu Live CD/USB and post the output of bootinfoscript as per instructions here.
http://bootinfoscript.sourceforge.net
While posting, click the # icon in post menu and paste your text in between the generated code tags.
Boot Info Script 0.55 dated February 15th, 2010
============================= Boot Info Summary: ==============================
=> Grub 2 is installed in the MBR of /dev/sda and looks on the same drive in
partition #2 for /boot/grub.
=> Windows is installed in the MBR of /dev/sdb
=> Syslinux is installed in the MBR of /dev/sdc
sda2: __________________________________________________ _______________________
File system: ext4
Boot sector type: -
Boot sector info:
Operating System: Ubuntu 10.04.1 LTS
Boot files/dirs: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img
sda3: __________________________________________________ _______________________
File system: Extended Partition
Boot sector type: -
Boot sector info:
sda5: __________________________________________________ _______________________
File system: ext4
Boot sector type: -
Boot sector info:
Operating System:
Boot files/dirs:
sda6: __________________________________________________ _______________________
File system: swap
Boot sector type: -
Boot sector info:
sdb1: __________________________________________________ _______________________
File system: ntfs
Boot sector type: Windows XP
Boot sector info: No errors found in the Boot Parameter Block.
Operating System: Windows XP
Boot files/dirs: /boot.ini /ntldr /NTDETECT.COM
=========================== Drive/Partition Info: =============================
Drive: sda ___________________ __________________________________________________ ___
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
Partition Boot Start End Size Id System
/dev/sda2 * 348,434,432 642,379,775 293,945,344 83 Linux
/dev/sda3 642,381,822 976,773,119 334,391,298 5 Extended
/dev/sda5 642,381,824 966,598,655 324,216,832 83 Linux
/dev/sda6 966,600,704 976,773,119 10,172,416 82 Linux swap / Solaris
Drive: sdb ___________________ __________________________________________________ ___
Disk /dev/sdb: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders, total 156301488 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
Partition Boot Start End Size Id System
/dev/sdb1 * 63 156,280,319 156,280,257 7 HPFS/NTFS
Drive: sdc ___________________ __________________________________________________ ___
Disk /dev/sdc: 8011 MB, 8011120640 bytes
247 heads, 62 sectors/track, 1021 cylinders, total 15646720 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
Partition Boot Start End Size Id System
blkid -c /dev/null: __________________________________________________ __________
Device UUID TYPE LABEL
/dev/loop0 squashfs
/dev/sda2 12479a15-9274-4044-a69e-6699415e2458 ext4
/dev/sda3: PTTYPE="dos"
/dev/sda5 68c13589-1d0f-41a4-96f8-f2e91ae4f903 ext4
/dev/sda6 16e4aa39-905a-411e-a7aa-0258b5624f48 swap
/dev/sda: PTTYPE="dos"
/dev/sdb1 123C18233C1803FF ntfs
/dev/sdb: PTTYPE="dos"
/dev/sdc: PTTYPE="dos"
============================ "mount | grep ^/dev output: ===========================
Device Mount_Point Type Options
aufs / aufs (rw)
/dev/sr0 /cdrom iso9660 (ro,noatime)
/dev/loop0 /rofs squashfs (ro,noatime)
/dev/sda2 /media/12479a15-9274-4044-a69e-6699415e2458 ext4 (rw,nosuid,nodev,uhelper=udisks)
/dev/sda5 /media/68c13589-1d0f-41a4-96f8-f2e91ae4f903 ext4 (rw,nosuid,nodev,uhelper=udisks)
=========================== sda2/boot/grub/grub.cfg: ===========================
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by /usr/sbin/grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
load_env
fi
set default="0"
if [ ${prev_saved_entry} ]; then
set saved_entry=${prev_saved_entry}
save_env saved_entry
set prev_saved_entry=
save_env prev_saved_entry
set boot_once=true
fi
function savedefault {
if [ -z ${boot_once} ]; then
saved_entry=${chosen}
save_env saved_entry
fi
}
function recordfail {
set recordfail=1
if [ -n ${have_grubenv} ]; then if [ -z ${boot_once} ]; then save_env recordfail; fi; fi
}
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
if loadfont /usr/share/grub/unicode.pf2 ; then
set gfxmode=640x480
insmod gfxterm
insmod vbe
if terminal_output gfxterm ; then true ; else
# For backward compatibility with versions of terminal.mod that don't
# understand terminal_output
terminal gfxterm
fi
fi
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
set locale_dir=($root)/boot/grub/locale
set lang=en
insmod gettext
if [ ${recordfail} = 1 ]; then
set timeout=-1
else
set timeout=10
fi
### END /etc/grub.d/00_header ###
### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
### END /etc/grub.d/05_debian_theme ###
### BEGIN /etc/grub.d/10_linux ###
menuentry 'Ubuntu, with Linux 2.6.32-24-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
linux /boot/vmlinuz-2.6.32-24-generic root=UUID=12479a15-9274-4044-a69e-6699415e2458 ro quiet splash
initrd /boot/initrd.img-2.6.32-24-generic
}
menuentry 'Ubuntu, with Linux 2.6.32-24-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
echo 'Loading Linux 2.6.32-24-generic ...'
linux /boot/vmlinuz-2.6.32-24-generic root=UUID=12479a15-9274-4044-a69e-6699415e2458 ro single
echo 'Loading initial ramdisk ...'
initrd /boot/initrd.img-2.6.32-24-generic
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
linux16 /boot/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
insmod ext2
set root='(hd0,2)'
search --no-floppy --fs-uuid --set 12479a15-9274-4044-a69e-6699415e2458
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 123c18233c1803ff
drivemap -s (hd0) ${root}
chainloader +1
}
### END /etc/grub.d/30_os-prober ###
### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###
=============================== sda2/etc/fstab: ===============================
# /etc/fstab: static file system information.
#
# Use 'blkid -o value -s UUID' to print the universally unique identifier
# for a device; this may be used with UUID= as a more robust way to name
# devices that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc nodev,noexec,nosuid 0 0
# / was on /dev/sda2 during installation
UUID=12479a15-9274-4044-a69e-6699415e2458 / ext4 errors=remount-ro 0 1
# /home was on /dev/sda5 during installation
UUID=68c13589-1d0f-41a4-96f8-f2e91ae4f903 /home ext4 defaults 0 2
# swap was on /dev/sda6 during installation
UUID=16e4aa39-905a-411e-a7aa-0258b5624f48 none swap sw 0 0
/dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0
=================== sda2: Location of files loaded by Grub: ===================
294.5GB: boot/grub/core.img
204.4GB: boot/grub/grub.cfg
294.5GB: boot/initrd.img-2.6.32-24-generic
178.6GB: boot/vmlinuz-2.6.32-24-generic
294.5GB: initrd.img
178.6GB: vmlinuz
================================ sdb1/boot.ini: ================================
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOW S
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect