From your description of your needs, I would suggest enabling a feature called "MAC filtering" on your router...basically, every wireless card has a MAC adress...sort of like an unique ID...find out the MAC address of the wireless card/device on your laptop, and enter it into the wireless router...what this will do is everytime somebody attempts to connect to your wireless router, it will first check if that wireless client's MAC address is inside its database, if not, it will not let them connect...if the MAC address matches, then the client is allowed to access the router...it does not provide any encryption of any sort, but is just an easy way to control or limit the people who are able to access your router...I think this is the feature that would best suit your needs...your sister would not need to manually input a password/user everytime she turns on your laptop and signs on to your network...the router will just automatically check if her computer is in its MAC address database and let her on appropriately...it is elegant, simple, and fits your need...look in your manual for "MAC filtering"...every router has this feature and it is easy to setup...

__________________
1995 black pearl/black Mercedes-Benz E420 :