user name/password trouble

I don't know for sure if this is the right forum, but we really need help in a big way. My son has a HP Pavilion sv6130us. He has joined some web pages where he has to sign in with a user name and password. He originally created these accounts on my laptop but as soon as we were able to connect his laptop also to the internet he tried to continue logging on to these web pages on his computer. His computer will not recognize his user name or password. He gets a message that they don't do together. He types them just the same as he does on my computer but it will never be accepted. I have contacted HP support and tried many different things. Deleting cookies, deleting files, reseting IE, resetting web settings. We have spent days trying to figure out why he can not sign in to these accounts on his computer. He contacted the creater of the web page and she has no clue as to why this is happening. He has to trouble getting on to the web page. His internet is working just fine, his email works just fine, he can even enter into chat on these pages but not as himself. He can not check his messages or write with his user name, or something like that. Anyway, please if there is anyone out there who may be able to help it would be appreciated. The object of his getting internet was so that he would not have to use my computer!! Thank you.

 

If he is using the correct Name/password combo - my next guess would be something in IE's settings is not letting him authenticate. Go through both PCs IE settings and see if they match...
Is his PC running a different firewall or pop-up blocker, or ad programs?