In addition, the power often doesn't go out cleanly, but with spikes and jitters both when it ends and when it comes back on. Like everything else, the more you spend, the better protection you get. You are throwing your money away. If you need to use an extension cord, use a proper one. Trying to save on an extension cord by cutting the grounding pin off your PC cord is not only going to cause you problems but is also dangerous.
Few people are willing to use their PCs with no protection at all.
The least-expensive, most basic form of protection is a surge suppressor. I for am not totally sold on them. I see plenty of computers that have been damaged from surges and they were on a surge protector. Cheap surge suppressors don't really offer very much protection. Good line conditioners can be quite costly due to the high quality of components required to do the best job.