You can if you have a NetBoot server set up. This requires control over your DHCP server (like if you use a full gateway server or you use DD-WRT or Tomato on your router) to set up where to find a PXEboot environment (easy to set up using dnsmasq), and then a server actually serving proper images over the network.
This is an example for a CentOS install handling both DHCP and PXE (using tftp and NFS):
http://wiki.centos.org/HowTos/DisklessClients
EDIT: And also Debian:
http://www.debian-administration.org/articles/478
For dnsmasq, the config line is: ('itchy'/192.168.1.50 is the tftp server)
Code:
dhcp-boot=pxelinux.0,itchy,192.168.1.50
So then you set up the HTPC in the BIOS to boot using the PXE environment, it will go initiate the network, look for the DHCP server which points it to the TFTP server and it netboots the image. The NFS is used for actual storage of media and user account files (any dynamic files).