Hi. Hope this doesn't come too late to be of help to you. As I understand it, with Crystal Reports open to the report you want to remove the Group Tree from, click on the Menu Bar... then click on "File", "Report Options", and in the dialog box that pops up, click on the checkbox labeled "Create Group Tree" to remove the checkmark. To make it effective, "Save", close, and reopen the report and the Group Tree should be gone, with the button grayed out that allows the Group Tree to be opened.
Note: This only takes care of the particular report you have open and active when you remove the checkmark. To change the Group Tree Default to "inactive" for any New reports, you need to click on the Menu Bar... then click on "File", and "Options" (not Report Options). In the dialog box that pops up, click on the checkbox labeled "Create Group Tree" to remove the checkmark. Any changes made in this "Options" dialog box affects every new report that is created after the change in "Options" is made. But existing reports will have to be changed as outlined above for the individual report.