Big BIG Issues

I need some big help here. My girlfriend's computer has turned on her. I know that the real issue is that she and her father aren't exactly aware of what to do or not to do with computers but felt that they were perfectly safe with a Mac. The OS is 10.2. She first noticed the problem after finding that she couldn't get onto the internet. The second symptom is that the clock and volume icon in the top right corner are flickering. As I began looking into the problem I first found that the admin password has been changed without anyone in the house touching it. Also, NOTHING will mount. No cd's, no disk images, no USB devices, nothing. It's really not looking good because they threw away the startup disk a long time ago and I can't even get things from my computer to work on hers. If anyone has any ideas please help me out with this.