Hi Matt/Alexander/Chris, Thanks for all the suggestions. The fix wasn't as drastic as re-installation of the operating system, system restore on Windows 7 did the job. What I did was quite stupid. I will be more careful next time. Thanks, Amitava Amitava Roy J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices (CAMD) Louisiana State University, Baton Rouge, LA 70806