2nd hand pro laptop but no password

Hello, I bought a second-hand Mac Pro laptop but there were no restore discs. I cannot use it because I dont have the password. The seller was to send all this to me but didnt. I have no way to contact her because she flunked her course at university and left the area. Hence the sale of her laptop!

How to I get into the files so that I can delete her stuff and use it myself. All I can access is her music,etc.
I bought it so that I could store my artwork and use the internet and it seems to be useless so far. Please help....otherwise it is a £600 white elephant

Bea