made a mistake on prewiring

I assume that you mean Cat5 for ethernet. If so, you could get some small 4 port ethernet switches to create little mini-subnets.

Did you staple them done or something? You could use one to pull more through if not. I try to alway pull wire "loose" through walls and then attach a heavy string so in the future I can pull more.

I wouldn't worry. I strung miles of cate 5e and coax only to find out most of what I implement is wireless. I've only hooked up 1/20th of what I strung.

How far is the wire, how thick is it, did it go through studs, how big did you make those holes, etc?

Could you use it as a "pull wire", and pull through a few more runs?

I'm not sure exactly what you're trying to do but remember that an ethernet connection only uses 2 of the four pair of a cat5. You can actually get two ethernet connections out of a single cat5 wire.

Put network switches everywhere.

http://*******.com/3csvwk

Check all of the networking vendors. Linksys, D-Link, SMC, etc. They make 4 or 5 port switches. A 4 port would give you 3 additional connections from one input.

I have an 8 port switch in my office where I have only one RJ45 in the wall, but needed more connections. Great quick solution for a couple more ports.