Vista - Can not access CD-rom content

Hi,

I am running Virtual Server 2005 R2 on my Windows Vista SP1 enterprise
edition notebook and I have the following problem:

I am able to attach\mount my physical CD\DVD writer as the cd-rom of my
virtual machine but when I add a CD or DVD to the physical drive the virtual
machine is not able to detect and read it ( although I am able to access it
through my physical machine). On the other hand If I attach\mount an ISO
image as the CD-Rom drive of my virtual machine, the virtual machine detects
it and access it without a problem.

What could be the reason that beside that I have attached my physical CD\DVD
writer to the cd-rom of my Virtal Machine I am not able to detect and read
the media that is in my physical dirve through my Virtual Machine and how can
I solve this problem?

Thanks,

--
Screech