My mistake, I was looking at the diagnostics for a newer Optiplex. I assume you mean an orange circle on the power button. An orange power button means the PSU is working, but the system doesn't process data. The following posts may help. I assume you cannot run diagnostics by tapping F12 when the system starts. It is possible that the motherboard is bad. The system is getting up there in age and it might be time for a new system.