Below given are the steps which I followed to install ubuntu 12.10 with existing windows 8 in my machine.

1. I downloaded ubuntu 12.10 into my disk and made it bootable from my usb by selecting that iso file.
2. Then restared my mahine and in BIOS I selected boot from usb.
3. Went into Linux os and selected install ubuntu alongside windows 8. It asked for memory allocation and I selected 550 GB for Ubuntu and 404GB for Windows. After that it completed ubuntu installation.
4. The booted into my windows 8 and used easyBCD to add a new entry. Ubuntu grup2

5. Now the easyBCD shows,

   There are a total of 4 entries listed in the bootloader.
   
   Default: Windows 8
   Timeout: 10 seconds
   EasyBCD Boot Device: C:\
   
   Entry #1
   Name: Lenovo Recovery System
   BCD ID: {e58d0cb6-2eae-11e2-9d20-806e6f6e6963}
   Device: \Device\HarddiskVolume3
   Bootloader Path: \EFI\Microsoft\Boot\LrsBootMgr.efi
   
   Entry #2
   Name: EFI USB Device
   BCD ID: {e58d0cb5-2eae-11e2-9d20-806e6f6e6963}
   Device: Unknown
   Bootloader Path: 
   
   Entry #3
   Name: Windows 8
   BCD ID: {current}
   Drive: C:\
   Bootloader Path: \windows\system32\winload.efi
   
   Entry #4
   Name: Ubuntu 12.10
   BCD ID: {6f173570-3bce-11e2-be74-c0143dd589c0}
   Drive: C:\
   Bootloader Path: \NST\AutoNeoGrub0.mbr
   

6. Next I restarted my system and in the boot options it shows windows 8 and ubuntu 12.10

7. When I click on ubuntu it displays,

   \NST\AutoNeoGrub0.mbr
   status 0xc000007b
   The application or operating system cold not be loaded because a required file is    missing or contains errors.
   

Can you help me resolve this...

Thanks :)