Do note that nothing can offer full protection from a direct lightning strike. I don't really recommend the use of surge and spike protectors because they are not much more than fancy and expensive extension cords. Instead, I recommend all computers be on a "good" UPS with AVR. These offer superior protection from all sorts of power anomalies, not just excessive high-voltage events like surges and spikes. But again, even the best UPS cannot protect from a direct strike.
The "paper-clip" test is not conclusive. All it does is allow the PSU to turn on. It does not show if the required output voltages are present, nor does it reveal the quality of the voltages. That can only be done by an experience individual using an oscilloscopic or power supply analyzer - expensive and specialized test equipment requiring special training to use and understand the results.
So for "normal users", I recommend swapping in a known good PSU or have theirs properly tested by a quality electronics technician.
Alternatively, you can try a PSU Tester
. The advantage of this model is that it has a LCD readout of the voltages. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within the required
tolerances as specified in the ATX Form Factor PSU Design Guide
(see “Table 2. DC Output Voltage Regulation” on Page 13). Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". However, none of these testers test for ripple and they only provide a little "dummy load", not a variety of "realistic" loads. So while much better than nothing (or a paper clip), using one of these testers is not a "conclusive" test either.