My Mac is a Macbook Pro 17", I got it from my friend (no original disc).
So after upgrading it to Mavericks (I was unable to install Windows using Boot camp of 10.6.8), Boot Camp successfully let me install Windows 7 Professional (x64).
The problem is that, I shrink the Boot Camp partition, and create another NTFS partition (so I can store data in the second partition as I usually do when using Windows). Now, I cannot boot into Mac OS anymore. Holding Command + Option + R does nothing, holding Option while startup shows a hard drive named Windows (instead of Mac HD). And no Recovery HD too