Well, after carefully looking around on the net and trying to find an easy asnwer to your question ...lol..ugh.....well.... Its like this - just get a cd-rom and MAKE a way to install one lol.
Or....
You can just use a cd-rom to get windows installed and the take it it back out, since you don't have room.
Is there a PC case inside the cocktail or did you just mount the motherboard inside it? I think that would help people understand why you can't put cd-rom in.
All in all though, i think its going to be a nightmare without cd-rom to work with in some fashion, as you would have to get some kind of dos boot disk with some kind of network drivers going before you could even think about trying to access the network from your main pc. From what i was readin while looking through google searches it just sounds like WAY too much of hassle and too many complications.
I know it wasn't much help, but its the best i can offer lol.
I will keep looking and maybe i will come across something.
You can look too on google and just type in something along the lines of INSTALL WINDOWS OVER A NETWORK or something like that and just start looking until you find what you are looking for

good luck man!
g~