How to change WordPress word into EdenTech.co.cc

Hi All I have just installed WordPress 2.9.1 in my personal site EdenTech.co.cc. But I find somethig to change in the setting ie when user register in my site the activation link is send to its email. But the sender name is WordPress and The subject field is EdenTech registartion activation. The Subject field is Ok but How to change the sender Address plz help???