1) UNINSTALL BY PROGRAM IN START MENU,
above Autodesk : name unin­stall tool

2) DELETE LICENCING FILE

On Vista or Windows 7:
C:\ProgramData\FLEXnet\adskflex_########_tsf.data
C:\ProgramData\FLEXnet\adskflex_########_tsf.data.backup
 
On Windows XP:
C:\Documents and Settings\All Users\Application Data\FLEXnet\adskflex_########_tsf.data
C:\Documents and Settings\All Users\Application Data\FLEXnet\adskflex_########_tsf.data.backup

3) DELETE OTHER FILES IN :

C:\Program Files\Autodesk\
C:\ProgramData\Autodesk\
C:\Program Files (x86)\Autodesk\
C:\Users\All Users\Autodesk\
C:\Users\**YOUR USERID**\AppData\Roaming\Autodesk\
C:\Users\**YOUR USERID**\AppData\Local\Autodesk\

SOURCE