Mac won't boot! Need OSX disc?

Hello,

My friend has a Mac G3 OSX 10.2 and he said it froze so he rebooted it. But now it won't load the OS, so I figured he has a corrupt system file and needs the OSX cd. (I'm a PC guy so I'm just guessing this is correct.) The only problem is that his OSX disc is over 400 miles away at his mother's house. Is their some other way to fix this problem?

The only OSX discs I can borrow are v10.3, would they work with his v10.2 computer?

Some advice would be nice. :)

You can boot from 10.3 disc and run Disk Utility without installing it ;)