iMac start disk m.i.a.!

[talkinghead]

Newbie question, I bought an iMac (late 09) from a ligitimate owner, however she misplaced the start (OS) disks. I think the only way to change the owner name on the computer is with the start disks, right? It's not absolutely necessary to clean off the drive, as she had nothing on it anyway, but I wanted to get my wife's name on it.
What are my choices here?

 

[MacHamster68]

if you want to rename this little drive icon on the desktop , just rename it with a right click -get info - name /extensions here you go name it whatever you want
for changing username just create a new user in system preferences --accounts once created give him admin rights and log in with it and delete that old account

and for the install disc just call apple they might send them to you , they did send me the original disc for my eMac from 2006 for just the postage cost