Sorry ericwu,
Yes, you are right, it was the window named 'Xilisoft Video Converter' that was causing the problem. I wrote 'Xilisoft ....' because I was using Ashampoo Uninstaller Platinum and yesterday I started using the Uninstaller's 'save files'. I didn't realize that this change would make the 'before' and 'after' comparison files run really really slow.
It was getting close to midnight and I was afraid to run out of time, so I wrote a quick message. I was certain that I was the only person that mentioned this problem because I found nothing about it on the Forums. The message was intended mostly to let people know that I needed no further assistance.
Again, I hope you'll forgive me for not following this thread through to the end. I'll be more careful the next time (if it ever happens)
AxCut