try running startup repair from a repair or installation disk. if that doesnt work, rebuild the bcd
To run the Bootrec.exe tool, you must start Windows RE. To do this, follow these steps:
Put the Windows Vista or Windows 7 installation disc in the disc drive, and then start the computer.
Press a key when you are prompted.
Select a language, a time, a currency, a keyboard or an input method, and then click Next.
Click Repair your computer.
Click the operating system that you want to repair, and then click Next.
In the System Recovery Options dialog box, click Command Prompt.
Type Bootrec.exe, and then press ENTER.
Note To start the computer from the Windows Vista or Windows 7 DVD, the computer must be configured to start from the DVD drive. For more information about how to configure the computer to start from the DVD drive, see the documentation that is included with the computer or contact the computer manufacturer.
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The Bootrec.exe tool supports the following options. Use the option that is appropriate for your situation.
Note If rebuilding the BCD does not resolve the startup issue, you can export and delete the BCD, and then run this option again. By doing this, you make sure that the BCD is completely rebuilt. To do this, type the following commands at the Windows RE command prompt:
bcdedit /export C:\\BCD_Backup
attrib bcd -s -h -r
ren c:\\boot\\bcd bcd.old