Hi, indeed, I found easiest was in Power Options set the Maximum CPU to 95%, 90%, or 85%, etc. Then use Intel Extreme Tuning to monitor the clock speed when running CPU stress tests (which will cause 100% CPU use).

This way, for example, a 2.9GHZ laptop CPU which normally Turbo Boosts to 3.5GHZ, 3.4GHZ, etc... will be "capped" at say, 2.6GHZ. Very nice, smooth, quieter, and especially if it is a fast i7 and you have an SSD... you won't notice the difference with CPU "underclocked" (capped) to lower than its rating.

Using Power Options as well I find is very safe, no need to mess with voltages, etc. and I believe there is no way it will put your warranty at risk, etc.