I had a system with windows 7 installed on it.
For installing Ubuntu 12.04 LTS, I installed GRUB.
Now Ubuntu is working fine. But the GRUB boot menu at system startup doesn't show Windows 7, after successful installation of Ubuntu.

Following is the output of `sudo fdisk -l` 

```
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 / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x71c30ce5

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              63       80324       40131   12  Compaq diagnostics
Partition 1 does not start on physical sector boundary.
/dev/sda2           81920    29044735    14481408    7  HPFS/NTFS/exFAT
/dev/sda3   *    29044736   522272767   246614016    7  HPFS/NTFS/exFAT
/dev/sda4       522274814   976764927   227245057    f  W95 Ext'd (LBA)
Partition 4 does not start on physical sector boundary.
/dev/sda5       522274816   651298815    64512000    7  HPFS/NTFS/exFAT
/dev/sda6       665636864   709464063    21913600    7  HPFS/NTFS/exFAT
/dev/sda7       808998912   976764927    83883008    7  HPFS/NTFS/exFAT
/dev/sda8       651300864   665634815     7166976   82  Linux swap / Solaris
/dev/sda9       709466112   808984575    49759232   83  Linux

Partition table entries are not in disk order
omitting empty partition (6)

Disk /dev/sdb: 32.0 GB, 32017047552 bytes
255 heads, 63 sectors/track, 3892 cylinders, total 62533296 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x71c30ccf

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *        2048    16775167     8386560   84  OS/2 hidden C: drive
/dev/sdb2        16777214    62531583    22877185    5  Extended
/dev/sdb5        16777216    54396927    18809856   83  Linux

```