Virtual Directory Support

hello,
This question was sent before but there is no good answer so :

When i see my phpinfo, Virtual Directory Support is disabled
How do I change this from disabled to enabled ?

I use php 5 and apache 2 on a linux FC5 server.

I also use a wampserver on a winxp workstation and here, it's enabled!!
I see all the configuration files. I can't see a difference!!

Please help me !! Thanks a lot.

Nico (French)