Updating to OS X 10.6.2 from 10.4.11 question

I'm currently running OS X 10.4.11 on a Mac Pro1, 1 that's almost three years old. I have 2 dual core intel xeon processors that run at 2.66 ghz. My roommate has just bought a new imac so I am in possession of his startup disk for OS X 10.6.2. The problem is I don't know tech stuff, and I was wondering if anyone here knows whether or not it's safe/possible for me to use his start up disk to put snow leopard onto my computer. Any help would be appreciated.

First, it would not be legal to use his disks as the system is installed on a computer already. Second, the install disks that come with a system are machine specific, and will not work with a different type of machine.

All right, that's what I thought, but I figured it couldn't hurt to ask. I don't have the $130 to shell out for leopard, and I'm finding it more and more difficult to work while still using tiger.