You asked this in another topic where you were asked to give the upload component that you are using.
What is the upload component that you are using and have you modified Web Wiz RTE configuration file to tell it to over write existing files?
To setup the Web Wiz RTE to overwrite existing files open in a text editor the file RTE_configuration/RTE_setup.asp and change the file below:-
Const blnOverWriteFiles = false
To:-
Const blnOverWriteFiles = true