Windows 7 installation went wrong - lost Mac OS X?

Hello,

PLEASE BE PATIENT AND READ WHOLE TEXT.

I went through the windows 7 installation process and i installed windows but unfortunately i can't find my mac os x anymore!

When i restart and press option key button black screen appears that lasts for 30 seconds (it appears too without pressing).

I guess that's for choosing the os but there is no any os there! No windows, no mac os x!

Just black screen for 30 minutes, then Windows starts up!

When i enter startup and recovery options in windows advanced system settings and look at the table: Choose default OS and click to change to MAC OS X, there is only Windows in it!

But the time while choosing the os is set to 30 sec, which is equal to the time of black screen that appears after turning on/restarting my Macbook Air.

When i look at my windows disk C memory it is just as i made with partition! 20 for Windows 7 OS and 26 (or close to it) free in diskc C

That means my 68 gbs (i left 41 gbs free for mac, and the rest was already used) are gone somewhere.

I followed installation guide and instructions very carefully.

I did partionining properly and didn't cancel anything!

After restart i chose disk for installing windows just like Boot Camp guide told me!

Can someone help me to find my Mac OS X or to somehow "factory reset" my Macbook Air!?

Kind Regards,