Ubuntu does not offers me "install alongside Windows" [duplicate]

Why don't I have this option?

here's my disk layout

sudo fdisk -l

Disk /dev/sda: 640.1 GB, 640135028736 bytes
255 heads, 63 sectors/track, 77825 cylinders, total 1250263728 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: 0x5b53cc54

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      409599      203776    7  HPFS/NTFS/exFAT
/dev/sda2          409600  1153767021   576678711    7  HPFS/NTFS/exFAT
/dev/sda3      1216962560  1250050047    16543744    7  HPFS/NTFS/exFAT
/dev/sda4      1250050048  1250261679      105816    c  W95 FAT32 (LBA)

Disk /dev/sdb: 4005 MB, 4005527552 bytes
32 heads, 63 sectors/track, 3880 cylinders, total 7823296 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: 0x20d8782d

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *          63     7822079     3911008+   c  W95 FAT32 (LBA)

The ubiquity installer offers to Install inside Windows when it cannot install alongside. i.e. when you already have 4 primary partitions used. This means that splitting the Windows partition is not possible.

If you select this option, it copies wubi.exe to the Windows Startup folder, so that when you next boot Windows it will automatically run Wubi.

Since you don't want to install with Wubi, you'll need instead to remove one of the primary partitions, and try installing again.

Here is an example of what ubiquity shows (although in this case the user has Windows XP, not Windows 7):

There are several possibles causes:

1. Your system already have 4 primary partitions:

   

   The solution is removing one.

2. Windows wasn't shutdown correctly. You must make sure Windows shutdown, no hibernation, no suspend, but a clean shutdown.

3. Your NTFS partition is dirty. You must check all your NTFS partitions for errors using:

   chkdsk /f c:
   

   For each partition, d:, e:, etc. Make sure you do this from Windows, not Linux.

4. If you are using Windows 8, disable fast boot. If you don't is like you are hibernating the system.

5. If Ubuntu installer reports an empty disk, it's more likely that you have leftover GPT data that needs to be removed.

In your windows system run a chkdsk on your disks for faults and relaunch Ubuntu installation.

And while you are in your windows system check your disks under Disk Manager (right click on Computer>Manage>Disk Manager) if it says that your disk is dynamic you wont be able to rezise them so the option of installing side by side cannot be handled by Ubuntu (is a Windows thing).

If you have a dynamic disk you have 2 options, format all and reinstall or use Microsft's own solution for converting dynamic disks back to basic. (note: ignore the title and body of that KB, go straight to the workaround). No warranties there!

The best thing is to backup your data and re-install Windows. When you are in the reformat drive screen you can choose to create new partitions. Always create at least 2/3 of the drive to be dedicated to the following:

[Windows XP][Free Space ---------------------------------------]

So you can create the following..

[Windows NTFS][-----------FAT32---for---storage----][Linux EXT4]