problems with installing elementary os luna

i m trying to install elementary os in my sony vaio laptop e series sve15127cnb. it has preinstalled windows 8. i tried to install elementary os with dual boot with windows 8. i downloaded 64 bit version from this website http://elementaryos.org/ and made a bootable usb with unetbootin-windows-608 software. when i rebooted my pc got the following option try elementary os install elementary os look for bad block(something like this) when i go in any of the options above i m only getting a blank screen and nothng else. i dont know wat to do? is this problem with some graphics or 64 bit. shall i try with 32 bit. because m getting only black screen and nothng else. what is the problem???????????