This really isn't an options but...
1.) Go to the DVD-ROM drive you want to use in My Computer
2.) Right-click it and go to properties, then the sharing tab
3.) Give it a sharename of dvd$
4.) Click OK and go to the PC you want to run the game on
5.) Open My Computer and select, tools, map network drive
6.) Select Drive letter E: from the list
7.) In the folder box type:
With machine name being the name of the computer the DVD drive is physically on.
8.) Now go to E:\ within My Computer and find setup.exe or similar. If you can't find the setup file, open the file autorun.inf in notepad, find the line:
Then find the file in E:\ where ever file.exe actually refers to
That will at least allow you to set it up. I don't know whether HL2 needs the disc in the drive to run though and it could be very jerkey if it does. I once tried DVD playback through a 10/100 and shared optical drive and it was jerkey to say the least lol. Thank god I upgraded to Gigabit