Trying to upgrade from 10.4 Tiger to 10.5 Leopard,

My friend gave me a file copy of Mac OS X 10.5 Leopard, and i'm upgrading from Mac OS X 10.4 Tiger, and when I try installing it, it just keeps asking me to restart the computer to initiate the installation. But when it finishes restarting, nothing happens, and I pull up the file again, and it asks me to restart once again. Basically, it just keeps asking me to restart my computer, and the installation is never initiated. Thanks.

If you are trying to use a gray OS X DVD (or a copy of one), it won't work. Gray DVDs have the drivers for only one model of Mac.

Well, my friend gave me a disk, it's not a disk per say.

That is even worse - known as piracy. It will not work.