Try this:
get the ip addresses of each of the computers you are working from (the name of the computer will also work for this)
to get an ip address: click start, click run, in the run command window type cmd and press enter. this brings you to a black dos window.
at dos type ipconfig
you will get an ip address of the computer you are on. write this down.
now from another computer that is on the network and click on the start button, then click run, and in the run box type //ipaddressfromtheotherpc/c$
it may then ask you for an id and password, here you would put the id of the administrator of the machine and a password if there is a password.
This will manually connect you to the other computer. you can also map a network drive if this works, by opening 'my computer', then click on tools, and choose map network drive. pick a drive letter to use, and for path put in \\ipaddressforothercomputer\c$ .. if you needed to put a password when connecting manually, click on the link 'connect using another computer' and put the id and password in here.