Question : sharing folders windows XP

hi all, i have a network with 12 computers, all sharing resources betwen us.

but i have 4 computer which i cant join betwen us in the network.

The computers can see other computers but cant enter the folders the messae says, you dont have permission, is really extrange because i dont have any fireweall, antivirus nothing, and i dont have a domain only WORKGROUP/.

only for testing i formatting one of them and reinstall windows, and have the same problem my computer cant enter the other bloqued computers.

any ideas ????

NOT Virus, Not Spyware are all clean

Answer : sharing folders windows XP

in the future, never give deny
this overrides all other permissions