Accessing Remote shares

How to access remote shares from an Windows Xp system?
I had win98 in my home and office pc. When i am at home i can access my office pc shares by its ip address like \\office pc ip\share name
now i have windows xp in my home pc and when i try toacces my office pc’s shares i get error that i cannot connect to my office pc. i have changed my home pc workgroup same as office but it doesn’t works and my office pc is directly connected to internet with a modem.
Can any one help me ?