Dual booting windows 8/Ubuntu 12.04.2, GRUB doesn't appear and Ubuntu never boots

I got a new ACER predator AG3620-UR308 which came with windows 8 and I wanted to run ubuntu 12.04.2 on it as a dual boot machine. The box came with 2TB HDD. So I made 4 partitions with a raw partition just after the windows installation partition.

I created a swap area and finished the installation. GRUB was installed on the only drive there which is /dev/sda.

After reboot, GRUB doesn't even come up. It always boots Windows 8. I repeated installation process twice and got the same result. I disabled secure boot from the BIOS and enabled CSM (don't even know what it means) according to Acer custhelp site . I boot from USB and got this:

$ sudo fdisk -l
WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't  support GPT. Use GNU Parted.
Disk /dev/sda: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 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: 0x8c361cb5
Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1  3907029167  1953514583+  ee  GPT
Partition 1 does not start on physical sector boundary.
Disk /dev/sdb: 8178 MB, 8178892800 bytes
255 heads, 63 sectors/track, 994 cylinders, total 15974400 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: 0x0006a87e
Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *        2048    15972351     7985152    b  W95 FAT32

Can anybody shed some light? thank you in advance

EDIT
I just did another trial with 13.04 this time and still no luck.

bios: secure-boot: disabled
enable CSM : always

• Deleted previous Ubuntu partition and swap area partition.now having free space


• Used usb installer to prepare usb with ubuntu-13.04-desktop-amd64.iso


• rebooted : liveusb didnt detect windows 8, used something else


• created partition ext4 for /


• created partition for swap-area


• default grub path is /dev/sda and clicked install

Acer always boots into windows.

NEW EDIT

After following the boot-repair suggestion installed on the liveUSB, I can now see grub but can't log into windows anymore as it's not in the list. The boot-repair also completed with an error, i guess logged on pastin.ubuntu

How my drive is organized

Try using Boot Repair in Ubuntu.

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Installing Boot Repair

1. Open the Terminal, then type:

   
   

   sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update




2. Press Enter.




3. Then type:

   
   

   sudo apt-get install -y boot-repair && (boot-repair &)




4. Press Enter

Using Boot Repair

Search for Boot Repair in the dash and launch it. Then click the "Recommended Repair" button and wait until it's finished.

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Reboot. It should work now, although your GRUB is probably littered with useless entries.