Again you're not quite explaining what youre trying to do, are you trying to copy files from pc to pc over the network? or Share a printer etc...? You still haven't told us which version of Windows your running. Are you talking about wireless?
Since you had your "network" running at some point, that suggests it shouldn't be too hard to fix. If you're running xp here some tips:
Make sure all pc's have DHCP assigned settings, if you assign them manually make sure they are on the same gateway, subnet etc...
All pc's should be on the same network name: mshome or workgroup or whatever you want.
Windows xp has a built in firewall, you might wanna turn that off. Cuz the pc's wont see each other.
Not much more I can tell you cuz you still haven't given enough info
goodluck