I would start another thread asking about coolers etc. (my feelings would be that the money spent on that cooler would be wasted on an fx4100, with an inadequate phase control motherboard)
the reason you had a single worker drop out is because of a lack of voltage.
now the fun part, you should really pause at 4.2 ghz and prime test for an hour+, and then read and read about overclocking.
I asked earlier about your voltages.
1. in bios
2.in desktop (zero load)
3. full load. (100%)
your desktop voltage (zero load) should now be different after disabling that feature. what is it?
theres a thing called LoadLine Calibration (LLC) which adjusts the difference between zero load and full load voltage drops.
you will have to read about this and learn as much as you can, this will give you the knowledge and power to get a stable overclock @ 4.3ghz and beyond.
heres a starting guide. http://www.masterslair.com/vdroop-and-load-line-calibration-is-vdroop-really-bad
your overclock @ 4.2ghz with 1.44 voltage is still over half a gig (600mhz) free performance. and for 24/7 use is good! amd recommend to stay below 1.5volts and so do most people.
I got to go sleep and well done on having the patience to test adequately between clocks.
remember to keep an eye on temperatures, frequencies and voltages when testing.......Edited by d1nky - 3/26/13 at 6:47pm