My netbook show Operating System not found. - Dell Inspiron Mini 1012 Netbook (IM1012799OBK)

SOURCE: My netbook says "Operating System

What were you doing prior to this error message ?
Did you try to install another OS or During installation did you abort the process
A clean installation of windows will resolve the issue

Or Try this

If you were able to start the computer prior to the issue, then try startup repair and check the result. To do this, try these steps.
Step 1: Perform startup repair using Vista DVD
a. Insert the Windows DVD.
b. Restart your computer.
c. Let the computer restart (boot) from the DVD.
d. If prompted, press any key to continue.
e. When you reach the Install Windows screen, select your preferences in the Language to install, Time and currency format, and Keyboard or input method boxes, and then click Next.
f. Do not click Install now. Instead, click Repair your computer. The System Recovery Options dialog box appears.
g. Make sure the correct operating system is selected, and then click Next.
h. After you click Next, the System Recovery Options menu appears.
i. Click Startup repair. Once the startup repair completes, click Finish to restart the computer.
j. Remove the DVD and restart the computer to see if the system starts fine. See Make system repairs from the Windows Recovery Environment
Also see http://support.microsoft.com/kb/932932 Go to BIOS (basic input/outputsystem (BIOS) and make hard disk as first bootable device. See BIOS: frequently asked questions
http://windows.microsoft.com/en-US/windows7/BIOS-frequently-asked-questions Important: Modifying BIOS incorrectly will cause serious damage.

Hope this helps