My suggestion as I get these all the time and repair the 2ghz model for people. First is one processor usually dies in the dual and will either show only one processor or lock up and crash when it tries to use that processor. I have some spares but they are heavy. I would suggest downloading and using ASD 2.5.8 and if a processor fails then that's of course what you need. If the processor shows up and tests don't error it out these machines are notorious for dust as air goes straight across and mucks up everything. Pulling out everything one at a time cleaning and reseating can fix a lot. The last thing that makes this a jacked up machine is the solder on the ram slots, they are small and weak. When they heat up they flex and bam unstable machine. Again the ASD may catch this, only fix for hat is reflow and that requires pulling he board and a hot air gun. That's risky but for free nothing to lose right?

Good luck

Once you figure it out they are a great machine, but the G5 systems just don't feel as snappy as the G4 units. They are fun though.

If it is a processor the 2 ghz have two or three model codes (different units made at different times) that have to be matched to work in th system.