\\computer is not accessible. You do not have permission etc etc

Hi, had this problem before and sorted it by downloading a server pack.. but cant find the solution I found before.. had a hard drive go down in each machine.. so ended up doing fresh installs.

Now, trying to get files moved from one to the other.. is impossible again.

its not the firewall, or antivirus.
I went thru all the fixes the last time, hence I know what will cure it.

Like I say, I installed like a server small progs pack.. and that sorted it all out.
Cant find the site I got the fix and download link from.
Anyone know what I'm on about?