You can always re-import students at any time until you have competitors or results, after which SportsTrak will object.
The reason SportsTrak does this is that the competitor list and results use the Student Code to relate back to actual students. If the student codes change, the relation is wrong and the data is screwed up.
If you really want to re-import the student file and you know that
The student codes will remain unchanged
The DoB is unchanged (for age based carnivals)
The Year Level is unchanged (for year level carnivals)
then you can re-import after renaming a couple of files.
1.Do a Backup, then close SportsTrak.
2.Rename Complist.tps to complist2.tps
3.Rename Results.tps to results2.tps
4.Delete Complist.tps and Results.tps from the current data folder
5.Run SportsTrak, Import Students (Replacing Existing Students), Exit SportsTrak.
The new students should have the same codes as previously but will have no points if results have been entered.
6.Delete Complist.tps and rename complist2.tps back to complist.tps
7.Delete Results.tps and rename Results2.tps back to Results.tps
8.Run SportsTrak and go to menu Utilities > Recalculate All Scores
If you cock up, you have a backup. And if you don't have a backup, consider yourself stuffed and don't ring us.