What will happen when I changed SATA OPERATION from RAID to ATA

You can install UBUNTU 12.04.5 LTS or higher in Side by Side mode using WUBI. Earlier Versions do not support Secure boot.

The Windows-based Ubuntu Installer (Wubi) allows you to install and uninstall Ubuntu from within Microsoft Windows. It lets a Microsoft Windows user try Ubuntu without risking any data loss due to disk formatting or partitioning.

Wubi requires Windows 98, ME, 2000, XP, Vista, Windows 7.

NOTE: Hibernation is not supported when installing Ubuntu via Wubi.

14.04 is the new LTS version. The Long Term Support (LTS) version of the Ubuntu operating system for desktop PCs and laptops, Ubuntu 14.04.3 LTS comes with five years of security and maintenance updates, guaranteed.

It resizes your NTFS partition and installs UBuntu in its own EFS partition.  When you reboot you can choose Linux or Windows.

• Ubuntu 12.04.5 alternate (64-bit) ›
• Ubuntu 12.04.5 alternate (32-bit) ›

• Ubuntu 14.04.3 LTS Desktop (64-bit) ›
• Ubuntu 14.04.3 LTS Desktop (32-bit) ›

Changing the Sata Mode will cause a STOP 0x0000007B INACCESSABLE_BOOT_DEVICE error.

https://support.microsoft.com/en-us/kb/922976

After you use the BIOS setup of a Windows computer to change the Serial Advanced Technology Attachment (SATA) mode of the boot drive to use either the Advanced Host Controller Interface (AHCI) specification or redundant array of independent disks (RAID) features, you receive the following error message when the computer is restarted: 

Hi, 

If you change the SATA mode from RAID to ATA, it could cause the operating system to become inaccessible since it was originally installed with a RAID configuration. You will most likely have to reinstall Windows.