Mshome workgroup asking for password?

Hey, I'm trying to set upa workgroup so that i can move files from my computer to my sisters laptop. I have already made it so i can access my shared folder on my other computer upstairs from this computer. but when i try to access this computer from the other computer upstairs it ask me for a password and i dont know what the password is because i have no password on this computer and i tried some general passwords like 'admin' and stuff but nothing worked. Where can i get the password? or better yet disable it? and the laptop is on vista home premium, what i really need is to be able to move files from this computer to my sisters laptop.

the image was taken off the computer upstairs (dining room) trying to access this computer (ryan)