WinXP Pro fault???

Am really very headache today…once finished set up the LAN access for my user’s 2 notebooks but then it was unable to access internet! I wonder is it due to winxp pro fault? I have a firewall so as usual i have set an ip address in the ie proxy setting.

Anyone could help me on this? I don’t understand why winxp always facing this kind of problem (happened once last year) whereas win98 or win2k no such problem at all!

Appreciate your quick reply. Thanks a lot.