I want to File share.

Well me i using Ubuntu right now and my sis laptop has windows Vista i know it sucks but what can i do. Anyways there is files and stuff i have on my Pc right now but they are kind of big to share on a disc if you catch my drift, well i want to file share but i can't or i do not know how to. any tips or help would be fine...also i tried it once but on windows every time they wanted access they need it a password or some key which i thought it was my password when i log in on Ubuntu but is not so help i guess? oh also can Ubuntu and windows file share anyways?