get an administrator password without changing it

I have installed Windows Vista on my laptop and I wanted to know if it is possible to access the password without changing the same because I want to run it on the standard user. My sister is not giving me password because I install too much of games and play it on the computer. She has also disabled any installation of any software or games. So, can anyone tell me how do I get a workaround with this sort of things that my sister is doing. Thank you for any help.

Well i would suggest you to have a look at the Petri's Recommended Windows Password Recovery Utility. I am telling you to choose this software because it is the one of the most important tool that I have come accross for password kind of things. You can get this software pretty easily by searching on the net, which will be able to give you administrator account login or so.