It's good that you switched back the voltage to default 2.2 volts, but you should set your processor to 3.5 X 100 MHZ because that's what the 350 is meant to function at, not 5.5 X 66 MHZ. That way you take advantage of 100mhz bus speed instead of 66 mhz.
Is your Trident video card agp or pci? and how much video Ram does it have?
As mentioned before, try a different video card (ie.ATI) and see what happens and see about finding newer drivers for your components if available.
Did you buy your AMD processor in a retail box or as just an OEM VERSION?
Are you using the first version of Win98 or the Second Edition version?

If all else fails, try a different processor (ie.Pentium MMX or classic) and test it on your current board to see if you have a defective processor? Processors are rarely defective.