There are certain ports needed in order to gain ILO and remote media access to an HP ProLiant system. The G7 systems use ILO3, so the general port cheat-sheet is:
List Forwarded iLO Ports
22 Secure Shell (SSH)
23 Remote Console / telnet
80 Web Server Non-SSL (HTTP)
443 Web Server SSL (HTTPS)
3389 Terminal Services
17988 Virtual Media
9300 Shared Remote Console
17990 Console Replay
3002 Raw Serial Data
In short, 23, 80, 443 and 17988 are the main ports you'll need access to in order to perform an installation through the GUI. Are you being blocked by a firewall? Do you have any way to get directly onto the ILO's network (assuming it's on a different network segment). I often end up using a convoluted SSH forwarding string to accomplish this at distant sites...
ssh -L 22:<iLO ip address>:22 -L 23:<iLO ip address>:23 -L 80:<iLO ip address>:80 -L 443:<iLO ip address>:443 -L 3389:<iLO ip address>:3389
-L 17988:<iLO ip address>:17988 -L 9300:<iLO ip address>:9300 -L 17990:<iLO ip address>:17990 -L 3002:<iLO ip address>:3002 user@gateway
There are other options, though. You can SSH to the ILO and force it to mount a .ISO file residing at a URL. From the ILO ssh interface:
vm cdrom insert http://192.168.1.100/path/to/Windows.iso
vm cdrom set boot_once will tell the ILO to source the .ISO from a specific location.
There's also a USB/KVM dongle that can be attached directly to the blade server. On is included with each enclosure. That would allow the use of a USB DVD drive, assuming someone has physical access to the server.