What's needed to install a software upgrade Friend of mine has a Powerbook G4.
He came across some install disks for 10.4.6, in an envelope, with a bar code on the back.

He's asking me if that's all he needs to install the software. 

Can anybody provide guidance on this?
This should be all he needs, the install is only one disk. But there may be some things that hold up the install:


If the disk notes its for a particular machine, it does a check to see if it is the correct type of machine. There are ways to get around this, but you usually you should use the disk that is made for your machine, or a retail copy. 
If it can't install, it shouldn't damage his current installation


If you give more information on what the disks actually say (like on the front, or a picture), it would help answer more.