Posted 11 September 2009 - 06:07 AM
You answered your own question as to what the issue is.
The router is yelling "HELLO?" and your wireless card is yelling back "I HEAR YOU!" that is your signal strength. When you open a browser your PC yells "HEY, I WANNA GO SOME WHERE!" and the router answers back "OK" and the information is let through the router in both directions, that is your connectivity.
In your case when you have security turned on, your router is answering back "YOU CAN'T GO OUT WEARING THAT" and you have no connectivity. Meaning you aren't wearing the correct security.
So there is an issue with the security between your router and your PC. That is what you have to check. Since your sister has no issues then I'd say its on your PC.
And just for a little FYI, the ipconfig command just returns the info stored on your PC not the AP.
Hope this helps
Associate in Applied Science - Network Systems Management - Trident Technical College