> Hello, I would like to known how change htttracks's
> parameters for:
> 
> Source: <http://www.trompette.be/viewtopic.php?t=800>
> Download with htttrack:  /viewtopic.php?t=800   <--
> preserve exactly the same url

viewtopic.php?t=800 is not a valid filename on windows.
So you can't. 
With a user defined structure you can generate file names like
viewtopic_t-800.php See <http://httrack.kauler.com/help/User-defined_structure>