Stream videos?

Ok so here is the deal: I have this desktop with windows 7 and a laptop with 7 and an old dell with xp not currently running but thats another problem. I want to use the older dell to play movies on my tv, but it has a small hard drive and i dont wanna(can't) store the videos on there. I dont want to buy another external hard drive either. Im wondering what i can use that is like the homegroup thing on 7.
I set up a ad-hoc network between my desktop and laptop and it sorta works. Its very choppy and i can only imagine its worse on an older computer.
Does any one have any ideas?

if you install Win7 on the old laptop, and join all of them to a homegroup, the old laptop can stream videos from the other PCs using Media Center or Windows Media player. You will need a wireless hub and at least 802.11G, 802.11N would be better.