Well, I am not sure how you have your networking setup. On mine, I get a seperate IP address for each machine, but if you are using dial-up without a normal network connection to the router, I am unsure of how that would work.
But if you can figure out the IP address for windows xp, you should use that, and if you don't have a password, remove the whole password field (I believe that it does not have to be there).
But to walk you through the command, mount allows you to, well, mount partitions or network shares into the filesystem. -t is the type of filesystem, which we are using cifs, the -o specifies additional options you are passing to the command. In our case the username, password and umask. I believe you don't need the username and password explained, and the umask will make all the files readable, writeable, and executable for all users. If you want that changed I would just google umask. Next we have the partition/network share we want to mount. In this case you start with the IP Adress and the network share name. Next will be the place in the filesystem you want it mounted to. This folder has to already exist.
Oh and you need to be root to use this command (which is another reason I use the umask, this way other users can use it as well).