Lenovo's T420s Thinkpads are affected by an annoying issue where the fan gets stuck at high speeds, as seen at http://forums.lenovo.com/t5/T400-T500-and-newer-T-series/T420s-Fan-noise-Issue/m-p/671903#M56332, even for very low temperatures.

Such a fast spinning fan produces excessive noise, which "forbids" the use of the laptop in quiet environments, for not upsetting other people. This is extremely frustrating in situations such as meetings or studying at libraries. The frustration is exacerbated by having paid more money for buying a premium notebook.

If Lenovo could fix this long standing fan issue owners of T420s laptops would benefit from a more quiet machine and could use it to its full potential, without resorting to workarounds for keeping the laptop "silent". Furthermore, Lenovo's engineers might be able to get useful insights for designing new laptops with more efficient cooling systems, thus combining the renowned quality of their notebook computers with the joy of using a silent systems.