You might need to recover grub.

1. Insert your Ubuntu CD, reboot your computer and set it to boot from CD in the BIOS and boot into a live session. You can also use a LiveUSB if you have created one in the past.




2. Install and run Boot-Repair




3. Click "Recommended Repair".




4. Now reboot your system. The usual GRUB boot menu should appear. If it does not, hold Left Shift while booting. You will be able to choose between Ubuntu and Windows.

If this doesn't work, use the terminal way. As you are not familiar with Linux, please copy and paste the code.

Open a terminal. As of Ubuntu 11.10 and 11.04, this can be done by opening the Unity Dash (you can click the Ubuntu logo in the top panel or use the Windows key on your keyboard) and typing in "Terminal", and clicking what comes up. On earlier versions, you can achieve this by going to Applications -> Accessories -> Terminal.

1.You are then presented with a standard bash prompt, type:

sudo grub-install /dev/XXX

where XXX is the device of your Ubuntu install. (eg: grub-install /dev/sdb). Hint: You can also use /dev/disk/by-label/ if the partition you installed on has a label. You can determine the /dev node for such a device by running:

ls -l /dev/disk/by-label/

This will give the output of something like:

lrwxrwxrwx 1 root root 10 Oct 16 10:27 data -> ../../sdb2

lrwxrwxrwx 1 root root 10 Oct 16 10:27 data2 -> ../../sda2

lrwxrwxrwx 1 root root 10 Oct 16 10:27 fat -> ../../sda6

lrwxrwxrwx 1 root root 10 Oct 16 10:27 home -> ../../sda7

lrwxrwxrwx 1 root root 10 Oct 16 10:27 root -> ../../sda1

lrwxrwxrwx 1 root root 10 Oct 16 10:27 swap -> ../../sda5

lrwxrwxrwx 1 root root 10 Oct 16 10:27 windows -> ../../sdb1

You can also use sudo fdisk -l if you do not see the /dev/disk/by-label:

$ sudo fdisk -l



Disk /dev/sda: 160.0 GB, 160041885696 bytes

255 heads, 63 sectors/track, 19457 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x0001bc54



   Device Boot      Start         End      Blocks   Id  System

  /dev/sda1   *           1       18725   150403072   83  Linux

 /dev/sda2           18725       19458     5884929    5  Extended

/dev/sda5           18725       19458     5884928   82  Linux swap / Solaris



Disk /dev/sdb: 15.1 GB, 15103033344 bytes

64 heads, 32 sectors/track, 14403 cylinders

Units = cylinders of 2048 * 512 = 1048576 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00068852



   Device Boot      Start         End      Blocks   Id  System

/dev/sdb1   *           1       14403    14748656    c  W95 FAT32 (LBA)

From here, find only the drive name, ignore the partition number, that is, for partitions labeled "root", "data2", "fat", "home" and "swap" it's all still just sda. This is due to the fact that GRUB is installed in the MBR of the drive, and not on a partition.

1. Now reboot your system. The usual GRUB boot menu should appear. If it does not, hold Left Shift while booting. You will be able to choose between Ubuntu and Windows.

Using the Ubuntu Alternate CD

1.Boot your system from the Ubuntu Alternate CD.

1. When the Ubuntu splash screen comes up with the boot: prompt, type in rescue and press enter.




2. Choose your language, location (country) and then keyboard layout as if you were doing a fresh install.




3. Enter a host name, or leave it with the default (Ubuntu).




4. At this stage you are presented with a screen where you can select which partition is your root partition (there is a list of the partitions on your hard drive, so you are required to know which partition number Ubuntu is on). This will be dev/discs/discY/partX, where the X is a partition number and Y is the number of the drive.

6.Now proceed as described in "The terminal way" above.

Hope this helps!!!