General :: Erase All Of Vista

I have recently installed ubuntu on a previously vista operated laptop, now i need to eradicate all of vista i care not for it at all, I've read some of the threads here and saw someone say something about ubuntu overwriting everything on my hard drive including vista, is that dangerous, easy, and the most efficient way of doing this. i also tried removing the partition of vista by following a response to a thread, using gparted but now im stuck and i failed horribly (very limited computer knowledge).