Running the startup repair tool

Run the Startup Repair tool by using the Windows Vista or Windows 7 installation disc or by using the computer's preinstalled recovery options.

To run the Startup Repair tool by using the Windows Vista or Windows 7 installation disc

If you have the Windows Vista or Windows 7 installation disc, follow these steps to use the Startup Repair tool:

1.	Insert the Windows Vista installation disc. Note The computer must be configured to start from a CD or from a DVD. For information about how to configure the computer to start from a CD or from a DVD, see the information that came with the computer.

2.	Restart the computer. To do this, click Start, click the arrow next to the Lock button, and then click Restart Note If you cannot restart the computer by using this method, use the power button to turn off the computer. Then, turn the computer back on.
3.	Set your language preference, and then click Next Note In most cases, the startup repair process starts automatically, and you do not have the option to select it in the System Recovery Options menu.
4.	Click Repair your computer.
5.	In the System Recovery Options dialog box, click the operating system that you want to repair, and then click Next
6.	In the System Recovery Options menu, click Startup Repair to start the repair process.
7.	When the repair process is complete, click Finish

If the above step does not fix the issue would suggest that you perform a System Restore on the computer to restore back the previous settings when it was working fine.

To use the Windows Recovery Environment, you must have the Windows Vista or Windows 7 installation disc. To start the Windows Recovery Environment, follow these steps:

1.	Put the installation disc in the disc drive, and then start the computer.
2.	Press a key when you are prompted.
3.	Select a language, a time and currency, and a keyboard or input method, and then click Next.
4.	Click Repair your computer
5.	In the System Recovery Options dialog box, click the operating system that you want to repair, and then click Next

In the System Recovery Options dialog box, click System Restore to restore the operating system to the restore point that was created when the program or the driver was installed.

Refer the below link for more information.

http://windows.microsoft.com/en-US/windows7/Restore-your-computer-from-a-system-image-backup