Turned my mac book pro on and a folder with a question mark just flashes

Question

TTurned my Mac book pro laptop on and all I get is a flashing folder with a question mark on the screen

Answer 1

Have you tried to boot in Safe Mode (keep the Shift key down while booting, until the Apple grey backdrop, spinning gear and progress bar appear)?
If you can boot that way, it means some third-party software is causing problems.
If not, try to boot in Single User mode (press the Command/Apple and S keys on startup), then type "fsck -y" (no quotes), press Enter.
You should get a return such as:
fsck_hfs: Volume is journaled. No checking performed.
fsck_hfs: Use the -f option to force checking
If you do, then your startup volume is accessible. Type "restart" (no quotes...), then press Enter.
If not, you can try the following command:
mount -u/w /
(there's a space between mount and the dash, no space between the dash and u/w, and a space between u/w and the slash sign).
There shouldn't be any visible return on screen after that command, but if you wait a few seconds, you could then enter the following command:
systemstarter
Then press Enter.
That could suffice to boot your system, but still not the graphical user interface.
When the prompt sign (#) returns, type "restart" (again, without the quotes), and press Enter.
Tell us how it went.