Vista Tutorial - USer account password/administrator permissions

OKay, so i just got vista and my cousin et up the accounts and my sister is the administrator. I wanted to download something from the web but i needed administrative permisisons, and seeing that my sister can be a total $@#^% sometimes she won't let me change me to the administrator for awhiel whiel id ownload the thing. I tried to figure out her password but no luck. I searched the web trying to see if there was a way around it, but nothing helped. Can anybody tell me if if can do something here?

I would suggest you speak to the administrator - your sister.

she wont listen to me

She probably has a good reason - ask her!!

You don't need to change to the administrator.
Ask her to give you administrative privileges too, you will both be administrators.

I seriously doubt anyone on this forum will explain how to gain unauthorised administrative privileges so maybe asking your sister would be the best thing to do.

Good luck