Using the neosmart Vista disk recovery you should see a window with the following information.
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1 Why your PC shows Operating System not found
2 Fix Operating System not found or Missing in Windows
2.1 Fix #1: Verify your hard drive status in BIOS
2.2 Fix #2: Rebuild the BCD using bootrec.exe
2.3 Fix #2: Use Easy Recovery Essentials for a guaranteed fix
2.4 Fix #4: Run Automatic Repair
3 Operating System not found on Sony Vaio Laptops
4 More Information
4.1 Support Links
4.2 Applicable Systems
You need to use step 2.2 to rebuild the Boot Configuration Data.