If you want to share the C$ drive to a LAN, then it doesn't matter whether you're using a physical server or a VM -- just use the normal Windows [In]Security model to share the drive via CIFS.
[Edit: If you need to access a CIFS network share from Ubuntu, see the Ubuntu wiki.]
If you want the host to be able to read a VM's drive, then the answer depends upon what OS the host is running, what version of VM-hosting software the host is running, and what OS and version the VM is running AND if the VM is running.
Quoting from the vmware-mount documentation:
VMware Disk Mount is a utility for
Windows and Linux hosts that allows
you to mount an unused virtual disk as
a separate drive or partition without
needing to connect to the virtual disk
from within a virtual machine. You can
mount specific volumes of a virtual
disk if the virtual disk is
After you mount a virtual disk, you
can read from and write to the mounted
virtual disk as if it were a separate
file system with its own drive letter
or mount point on your computer. For
example, you could scan the disk for
viruses or transfer files between the
host system and a powered off virtual
machine. When you are finished using a
mounted virtual disk, you should
unmount it so the virtual machine can
use its virtual disk again.
If you're not using VMware Workstation, or not using the right version of VMware or Windows or Linux, you'll need to find a different approach.