What do you mean by your "Windows 7 is missing"? What happens when you turn on your computer? Do you get a blank screen? Can you log-in to the admin account?
In the meantime, here are the descriptions and step-by-step instructions on performing the system recovery options (as WR2 pointed out) in Windows 7 - http://windows.microsoft.com/en-US/windows7/What-are-the-system-recovery-options-in-Windows-7
Microsoft Windows Outreach