Playing DVDs/installing programs over networked drive?

Hello, I have a media center/extra LAN-computer where I have to chose between two generic PSUs, one which supports graphics cards (has 6pin), and one which has molex/4pin (for an old dvd-drive). Naturally, I first tried to do it with a networked drive (go to computer on main rig, right click on dvd, share), but I could only open text documents (EULA, readme, etc) and not the setup file. I switched to the other PSU so I could install the program (in this case HALO: Combat Evolved, if that matters) using the local drive. This worked fine. I tried putting in a DVD movie in my main rig, and while I could open the disc (and see a bunch of .vob or something files) I was not able to find a way of playing the movie.

For the convenience of running a graphics card at the same time as having access to disc media, I want this to work. In the future I plan to get a netbook, but if I can't install programs from discs, I might have a problem... Some programs I want are only available as discs, unless I turn to piracy (which I don't want to do).