Help ! i am confused

Every MacBook Pro comes with OS X on it.

If Mac OS X was erased from the system and has only Windows 7 on it, then unless there still remains the original partition for Mac OS X, unless someone else here knows of a different workaround, you will need to erase the drive (formatting it as Mac OS X Extended), install Mac OS X from the disks that came with the Mac, then use Boot Camp to create a new partition for Windows and reinstall Windows 7.

If there is indeed still a second partition, you should be able to install Mac OS X on that partition.

If the original owner claims that Mac OS X is still installed, try booting the Mac and hold down the Option key. If Mac OS X is indeed still installed, you should be able to see and choose that partition to boot from. If Windows was installed correctly, there will also be a Startup Disk control panel from which you could select the Mac OS X partition from which to boot.

http://support.apple.com/kb/HT3777

Regards.

P.S. Unless you know and trust the seller, I'd recommend erasing both operating systems and reinstalling anyway. You just have no way of knowing what sort of unlicensed software or even malware or keylogger might be installed in the system if you're just using it as the seller gave it to you.

Message was edited by: Dave Sawyer

The option button is the one right next to the command key.

Glad you worked things out. As a new Mac user, you might find the following sites helpful for future questions, particularly those of a basic nature:

Mac 101

and if you're coming from using Windows:

Switch 101

and an independent site many people find helpful:

My First Mac

Regards.