Modify the From section of email sent by WPMU to the user when a blog is created


Still new to WPMU 2.8.4a.

When a blog is created an email is sent to the user with the following info:

Subject: [] Your username and password
From: "WordPress" <>
Username: urb3
Password: b4f2e4f8

I would like to modify the "From: WordPress" part. I want to modify WordPress for the site name.

Browsed a lot for the topic on WPMU Forums and can't find which file and which variable do I have to modify.

Any clues will be appreciated.