Hey 2NR... It took me a while to figure out what you meant by "pw", and I understood (finally) "password".
I did a little research and there are two ways to this, if I am not mistaken, but I will give you the simplest way.
First, try this: restart the
laptop and keep pressing F8 until you get the OS Choices menu, select "Safe Mode". When safe mode is loaded click on Administrator and It should go to the Desktop but this depends if the Administrator account is enabled or it will not work.
Now, if this didn't work, here's your second method. For this, you will need a PC and a blank CD-ROM (regular 700mb should be good).
Since you are on your brother's computer, go to the following site:
Crack Windows XP or Vista Login Password [How To] | Windows Tools, Help & Guides
And follow the instructions. This should crack your password and you should be able to find your password again :P
Now I wish to apologize to all admins if this post is not allowed. But, if this method works, you got the password.
Good luck and tell me how it went.
-Dark Daxter