macbook 2012 not booting from internal drive but booting from external usb drive

hi everyone!!

here is what happened:

i have worked all day on my macbook pro, normally. when i got home and turned it on (i always power it off for rolling with it) it just didn't load the OS.

i run mavericks on a i7 mid 2012 macbook pro 13". it had an accident on last december and fell on the ground, but i've changed the hdd and it worked normally until last week when this happened.

i have a copy of my system on a usb drive and tried to start up from it and it worked.

i took my hdd from inside the lap top and started from it (yes, the same hard disk that was inside the machine) and it worked.

i took the macbook to an apple store and the "apple genius" that was there started up my machine from inside with another hdd running yosemite that they have in the store for testing.

today i bought a new hdd and put it in. but i can't format it or install the system. i had these 2 errors on disk utility

"partition failed with the error: wiping volume data to prevent future accidental probing failed"

and

"restore failure an error (32) occurred while copying. (broken pipe)

so:

it loads from my internal drive, but only when its connected via usb

it loaded the apple store drive internally

it does not format my new drive nor install the system on it

ANY suggestions, please??? it's really difficult to me to solve this problem...

thanks a lot!!!