How to customize the EditForm.aspx when you Edit a list item in a SharePoint 2007 list (EditForm.aspx).
When you want to enter a edit item into, let’s say, your Issue Tracker list, SharePoint calls upon the EditForm.aspx page for that list. The page contains a customized List Form Web Part that displays default columns associated with the Issue Tracker list properties. The Edit Item form cannot be edited within the browser, so in order for us to accomplish this we have to use SharePoint Designer 2007 tool. Here is the following link that i found how to do it. The blogger explain it for NewForm.aspx in very organized way. In case of EditForm.aspx is the same.
http://sharepoint07.wordpress.com/2008/02/05/customize-the-newformaspx/
Do the following steps to create and customize new edit form:
1. Open your site in SharePoint Designer.
2. Browse to your list and open the 'EditForm.aspx' web form.
3. Go File > Save As... and give the form a new name such as 'EditForm2.aspx'.
4. Delete the default List Form Web Part from the page.
5. Go Insert > SharePoint Controls > Custom List Form.
6. In the List or Document Library Form dialog, select the appropriate list, content type and type of form.
7. Click OK and a new Data Form Web Part is added with controls representing all the fields from the list (in my environment all the controls show "Error Rendering Control" but this does not affect the final result).
8. In the newly added Data Form Web Part, delete the rows containing fields not to be shown / hide to the user (ensure that fields being removed are not required fields without default values as this would prevent the user from submitting the form).
9. At this point, you can do other customization such as rearranging the fields if you wish.
10. Save the site