Question : 20 lab computers can't connect to the internet

Windows xp - workgroup.  They are able to ping to the router - no problem. IE doesn't work though.  They took their address from dhcp yesterday at 7am. They worked through the morning but then internet browsing failed around noon.

I can't answer what changed at noon.   I have to assume anything is possible.  Physical layer, is clearly working.  When I try to renew the address it takes ARPA addressing so they are unable to renew the address even though they were able to get dhcp address yesterday morning.  

All of the other computers on the network can access the internet no problem.
 
I don't expect anyone will be able to solve this with the few details I present here but I need more clues. Need help defining the problem

Answer : 20 lab computers can't connect to the internet

try
ipconfig/release
Followed by
ipconfig/renew.
This will renew the IP Address.

Now getting back to the main problem -
We need to work out whether it is a DNS issue or a routing issue.
Ping 4.2.2.2, if successful it means the issue is pointing to DNS and if not successful we will have to do some isolation tests