Removing hours from a Project file without impacting dates

[Huron43]

I have a Project file where there are hours loaded into the tasks. I want to
remove the hours without impacting the Start and Finish dates on the tasks.
When I try doing this, a before and after comparison of the Start and Finish
dates show they have changed. I have tried setting all the tasks to Fixed
Duration, but I still have the problem of the start and/or Finish dates
changing.

 

[Steve House [MVP - MS Project]]

When you say "there are hours loaded into the tasks" what exactly are you
referring to? Are you saying there are actual progress hours posted to them
or do you mean resources have been assigned to the tasks and man-hours of
effort computed for them? Or do you mean something else, like estimated
hours of duration have been specified (your reference to "fixed duration"
makes me wonder if that's what you mean)?