You should have a recovery partition on your system. You can get to it by tapping F8 during boot up. Please note that in Windows 10 Microsoft has been the boot process a lot faster which makes it harder to get to the recovery menu so don't be surprised if it takes a few reboots to get to the menu. It's even harder to get to it if you have a SSD drive. If you have an install disc or usb you can also repair from that.