Basim --
Two possible approaches you could use are:
1. Create a new project and manually enter all of the tasks into the
project. Set Durations, task dependencies, and constraints as needed. For
the in-progress tasks, enter an Actual Start date to match the Actual Start
date in the current plan, and then set the % Complete value to 20%. After
doing so, save and publish the project using Collaborate - Publish - All
Information. Then select the tasks that are in-progress and click
Collaborate - Publish - Republish Assignments and then click OK. This last
step will "push" the 20% complete information to each user's timesheet. Ask
your Project Server administrator to delete the old project from the Project
Server database.
2. Save the current project as an .mpp file and then ask your Project
Server administrator to delete the project from the Project Server database.
Rework the .mpp file until it reflects your new project management needs.
DO NOT cut and paste tasks in this plan. If you need to move a task, then
move it by grabbing the task's row header and drop it in its new location.
Save the final changes to the .mpp file and then close it. Import the .mpp
file into the Project Server database using Tools - Enterprise Options -
Import Project to Enterprise. Save and publish the project using
Collaborate - Publish - All Information. Then select the tasks that are
in-progress and click Collaborate - Publish - Republish Assignments and then
click OK. This last step will "push" the 20% complete information to each
user's timesheet.
A couple of thoughts. Perhaps someone else will have some additional ideas
for you. Hope this helps.