Well best of luck my friend

One other thing you might try if the new battery does not fix it:

This is an AMD Socket A board? so it should support both Athlon AND Duron processors?

There should be a jumper switch on the MoBo to change the FSB clockspeed................try setting it to the other setting, which I suspect will be 133 (perhaps 166?).

I know that Durons run at 100, and you will get the black screen if you set it any higher. It must be at least 6 years since I last saw that. From what I recall the default settings on Athlon/Duron MoBos were for the Duron.

What I don't know is how this unused system would react if it were effectively underclocked?

It is worth a try because it will only take a few moments and will not do any harm.