windows xp networking

HI !
FIRST OF ALL THANX FOR YOUR THIS SERVICE. I AM ALREADY MEMBER OF YOUR THIS SERVICE.BUT I WANT TO ASK YOU A QUESTION ABOUT WIN XP NETWORKING.
I GOT A COMPAQ NOTEBOOK AND IT IS CONNECTED TO NETWORK.I CAN’T REACH THE OTHER NETWORK COMPUTERS.AND I CAN’T PING TO ALL.BUT MY NETWORK LINE WORKS PROPERLY.I HAVE CONNECTED ANOTHER COMPUTER TO THIS LINE IT HAS WORKED.AND I CAN REACH THE INTERNET WITH NOTEBOOK USING WINXP VIA ANALOG X PROXY PROGRAM.
MY QUESTION IS THAT:
HOW CAN I PING AND REACH OTHER COMPUTERS WITH XP?
THE IP ADRESSES IS LEGAL AND TRUE.I KNOW IT BE COZ OTHER COMPUTERS PINGING PROPERLY.
THANX FOR CARE AND WAITIN FOR YOUR REPLY .
MY BEST REGARDS
DENIZ OLMEZ