To help you, a little more information is needed. Are the three computers connected to a cable/dsl modem through a router or do you have the other two computers connected to the XP2 computer which has access to the modem? If it is the latter, you will have to go into the firewall and ajust the IP addresses so that it can recognize the computers attached to the XP2.

I have Win-xp sp2 installed, I have been useing this for three weeks, all can get online, but now I found the other two user can not get online. All 3 user are admin. Can any one tell me the where the problem is or where I should look into.
 
Vooster
 
This is only one computer with 3 user name. Let say the user name is user1, user2 and user3. Only user1 can get online now.
but before all three users can get online, but all of a sudden only user1 can get online. I am useing Shawcable to get online.
Could it be a virus, or adware or something the other user installed?
 
This is the 2nd time this had happen.
The last time it happened, I format the drive and istalled a fresh copy of Win-xp sp2.
 
Three weeks laster this happen again. What is going on here.

Just a stab in the dark here, but check the XP firewall settings for the other two users...?
 
Rgds
AndyF