my mac book pro is showing a white screen with flashing ? on start up
Start up on Mac Book pro shows a flashig ? sign and wont start up
See that topic of
About the screens you see when your Mac starts up - Apple Support
It means that a startup/bootable device can't be found.
If the action in the link do not solve the problem:
- Boot to recovery
OS X: About OS X Recovery - Apple Support
and repair the startup disk
- Next reinstall Yosemite via Recovery
If you can't repair the startup disk the means the disk failed and has to be replaced
This is the Mac Pro desktop forum. I requested your post be moved to the MacBook Pro laptop forum.