Server 2003 Enterprise SP1 folder shares

Hi all,
Can someone please help.
All we want to do is stop some of our client PC's entering certain folders on the server.
Whats the easiest way to setup permissions on a particular folder.

On the server there is a folder called 'Work' (c:\Work) which is shared. All we want to do is allow only one client PC to beable to enter this folder and block everyone else.
It used to be so simple on windows 2000 server !

Help please !

 

Do you need to allow access to only a certain user or computer?? Either way it is the same method. right click on the folder select security and add the user in, if it is a computer then you may need to click on the objects button and tick the computer box as it is not there by default