When starting my MacBook, I'm getting flashing '?' mark. I had Win 7 also on it. Now I can see only Windows partition if I hold botton 'C' at start up. I cant reset PRAM also by holding command+option + P + R . I'm not worried about data. I need to do clean installation.
migrated from stackoverflow.com May 29 '11 at 4:48
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This is always a hard one. Try using your MacOS X CD to run Disk Utility and check / repair the disk. This and other steps are described here at the official Apple faq.
The problem is they don't guarantee much. If holding the Option Key only lists the Windows partition, then there's no other choice but to fix the problem so that the macbook can again "see" the Mac partition (and if so, you'd be unlikely to continue having the problem.)
On second thought, if following the above steps from Apple yields no solution, your last resort is to try Disk Utility anyway, to wipe the whole disk and start freshly. BUT...that will kill your Windows install too. However, it should be straight forward.
A flashing question mark means that the computer could not find the operating system. Can you boot from a Mac OS X installation disc? Is the system set to boot from the correct device? Hold the Option key as the system starts to access Startup Manager and select a boot device; try doing this to boot from the Mac OS X install DVD.
On a side note, if the computer was able to find the operating system but was corrupted, then it would have displayed a prohibitory sign, or a "no" sign, instead.