How to restore OS X after installing Windows in a single boot configuration
You can restore OS X in Internet Recovery Mode if you have a newer Mac:

Boot to Internet Recovery Mode by pressing altcmdR. The prerequisites for an Internet Recovery are listed here: Recovery/Internet Recovery.
In a few words you need the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated for a successful internet recovery.
On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot to the Recovery Netboot image which is loaded from an Apple/Akamai server.

Open Disk Utility and partition your internal disk: GUID partition scheme (use the &quot;Options...&quot; button at the bottom of the main pane for this), one partition, journaled HFS+.
Sometimes Disk Utility won't allow you to erase the internal disk: open Terminal and enter diskutil umountDisk /dev/disk0 and dd if=/dev/zero of=/dev/disk0 bs=512 count=1. Then retry to erase the disk with Disk Utility.

Close Disk Utility

Open Restore OS X and restore the original OS X. This will restore the OS X version your Mac came with.

After rebooting and configuring your Mac open App Store, download and install Mac OS X Mavericks (if an older OS X version was installed previously).