Can't boot Windows 7 after installing Ubuntu

Run fdisk -l on terminal to check the windows partition.

If you found it, then type update-grub

Then reboot

And you will able be able to choose your selected OS

If permission is denied on running fdisk -l alone, add administrator privileges by entering you password after writing this code into terminal sudo fdisk -l

I had the same problem! After starting the computer the GRUB Boot loader displayed UBUNTU and 2 further entries but not Windows. After long trying I succeeded by performing the following steps:

• Find out on what hard disk and what partition WINDOWS is installed.

• This you can do after opening a terminal and type at the prompt

  sudo fdisk -l
  

  (this must be done with administative rights, so you will be ask for your password). You will now get a table of your partitions with device names like /dev/sda1, /dev/sda2 .. and so on.

If you have installed windows it might have type NTFS. This means if the second entry in this table is like this:

Device...Boot.....Start...End......Blocks......Size .........Id.....System    
/dev/sda1..*...2048..467118879..467116032..222,8G   ..7.....Linux    
/dev/sda2 ..467118080...961144831....494026552..235,6G  7.....HPFS/NTFS/exFAT    
/dev/sda3 ..1270138878...1953523711..341692417..7,6G        5.....Extended    
/dev/sda5 ..1270138880...1945182207..337521664..7,6G        83....Linux

windows is installed on the second partition of the first hard disk (sda2)

(In my case both operating systems were installed on one hard disk with 2 partitions, on the first I had installed UBUNTU and Windows 7 on the second. ) Press C for accessing the GRUB command prompt. At the Grub-Prompt enter the following 3 commands:

Grub>   set root=(hd0,2)
Grub>   chainloader +1
Grub>   boot

Notice: In the command set root = (hd0,2) after hd type the (zero-based) number of the hard disk (here 0 ) and after the Comma the Number of the partion (here 2) . If your windows partition is sdb1 you must type set root=(hd1,1) if it is sdb4 type set root=(hd1,4) etc…

Now Windows should boot!

Now you might want to have Windows 7 permanently as a menu item in the GRUB Boatloader menu. This you can get as follows:

menuentry 'Windows 7' {
   set root=(hd0,2)  
   chainloader +1  
   boot
}

Save the file and close it.

Open a terminal and type on the command prompt:

sudo update-grub

After restarting my computer I got a further entry with windows 7 in the GRUB menu, so I can chose between Ubuntu and Windows.

1. First, restart your PC or laptop.

2. After restarting you see the Grub menu. Select Advanced Options for Ubuntu (with the arrow keys; press Enter to confirm).

   

3. In the Advanced Options menu you will see an entry Recovery Menu that you need to select.

4. Carefully select the grub – Update grub boot loader option.

   

5. It will automatically add an entry for Windows 7/8/10 to the boot menu.

6. To restart, press Ctrl+Alt+Del.

7. The system will restart and you finally have a option to select Windows 10/8/7. Select Windows and finally you have with your Windows OS.