If the above steps fail then you may try the clean boot procedure and check if its works.
To help troubleshoot error messages and other issues, you can start Windows Vista by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
Refer the below link to know more about clean boot procedure. How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7 http://support.microsoft.com/kb/929135
Reset the computer to start as usual
After you have finished troubleshooting, follow these steps to reset the computer to start as usual:
• Click Start, type msconfig in the Start Search box, and then press
• If you are prompted for an administrator password or for confirmation, type your password, or click
• On the General tab, click the Normal Startup option, and then click
• When you are prompted to restart the computer, click Restart.