Certain Macbook Pro has hardware issue relating to video. Such machine fails to book.

Following is the link to the issue.

http://www.apple.com/support/macbookpro-videoissues/

Following is the link to check your serial number:

https://checkcoverage.apple.com/us/en/

Find your machine’s manufacturing date and cross check against the first URL.

To get the data out:
check out this page

Have fun!!