Since Beowulf was born in 1994 and NASA constructed the first Beowulf cluster using IBM PCs, several schemes have been developed. This type of clusters allows high-performance parallel computing using low-cost PC hardware. Through this work we have designed and implemented a new operating system for the automatic construction and installation of a Beowulf parallel computing cluster. In particular, the paper presents the operating system and provides an easy way to construct a parallel computing cluster using this technology. The system is capable to support up to 254 computers and it is aimed to provide an environment in which any parallel computing application target may be built instantly from anywhere by anybody. In this sense, the main objective is to provide the researchers with an automated and easy to use tool for constructing low-cost parallel computing clusters in their own laboratories as a way to solve concrete problems or as a previous step before launching the code in a large computing facility as Blue Gene or MareNostrum. The system is fully functional and it can be obtained and distributed in a gnu license basis from the group website: www.ehu.es/AC.