i am trying to make my old pc a server and iam using centos.
my server will connect directly to internet and through a hub will give connection to other pcs in a small home network. so i would like to ask some help how i can do that
also i want to share a folder in the network with samba the other pcs have windows but windows cannot acces the samba thanks

I don't really understand what your question actually is...

You should be able to do all of this with linux centos. If I undertand right, you want one end to be connected to the internet and one end to your home network. Just configure the "internet end" as usual, but assign a static ip to you "home network end", so you will then be able to run a DHCP server on that side.
If you want your "clients" to connect to the internet trought this computer, you will also need to setup a small iptables script to perform NAT. Just search google about "iptables", "masquerading" and "natting", you should be able to find plenty of tutorials.

About your samba question... well, some details might help?
What have you tried so far? What are the symptoms?
Do you get any error messages? If so, what does it says? Do you "see" your linux computer from windows? If not, are you able to ping your linux computer? If so, are you able to access the share using the ip address instead of the name? Can you access a windows share from linux? Can you access your linux share from the linux computer (itself to itself)?

finally i got the solution the samba didn't work because of the firewall and i used firestarter to do the nat