Name Change

Williamsfrank: If you un-check the "Preserve previous name on existing credits", it will list all your old credits by your new name.

However, that is probably the incorrect thing to do. 

Suppose all your old work had been listed under the name "William S. Frank" and you change your name to "Dave J. Pizza". If you un-checked the "Preserve previous name on existing credits" box , then all your past credits would be listed on IMDb as having been worked on by Dave J. Pizza, with no indication that you used to be known as William S. Frank. Any IMDb contributor who reviewed the credits of your old films would see this as an error, presuming that Dave J. Pizza had taken credit for work not done by him but by William S. Frank, and not realizing that both names referred to the same person.

Rather, you should check the box marked "Preserve previous name on existing credits". This way, your past credits would be shown with the name Dave J. Pizza, but with an attribute of (as William S. Frank) to indicate that you are the same person who has changed his name.

In neither case, though, would checking or un-checking the box cause all your past credits to be removed from your page.

I hope this helps.