Restore GRUB after installing windows...

Installing WINDOWS with an existing LINUX changes the process of bootloading.
The GRUB loader however remains in the system and needs to get restored so that it can be listed in the OS selection menu.

Here are some simple steps to restore GRUB

i) Insert Ubuntu CD in CD-ROM.

ii) Boot the system from the begining and press ENTER to get this screen menu

iii) Enter the menu and you will automatically get access to ubuntu as a guest user.

iv) Go to Terminal and follows these simple steps -:

• go to Appliactions -> Accessories -> Terminal
  
• type sudo fdisk -l
                      
   
• mount the linux partition , type sudo mount /dev/sda5 /mnt
  where "/dev/sda5" is LINUX partition (highlited above) and partiton is mounted to "/mnt".
  
• Install GRUB
  type sudo grub-install --root-directory=/mnt /dev/sda
  u'll get a message for installation completion.
  
• Unmount the mnt
  type sudo umount /mnt
  
• Restart the system and remove the Ubuntu disk from CD-ROM
  and u'll get ur Ubuntu back . :-)