Power Mac G4 Doesn't Go to Sleep.


Power Mac G4 AGP graphics 20 g 450 processor with an internal iomega 100 zip drive running OS 10.2.6.

Everytime we tried to put the computer to sleep the power button starts turning orange and the zip drive turns on a green light, right after that, the computer wakes up completly not allowing the computer to go sleep.

What can I do to fix this problem?.
Isn't bad for the computer to get shutdown a lot or to stay active for most part of the day?.

I would appreciate any help.