Big bertha as it is named is a pc for anyone who likes thier gamming at good fps and at a good price. Thier is no operating system in this part list as i installed my own one which i already had. Everything in the pc works and fits without too much bother but the cooler master was a bit of a task to fit so i would recomend getting someone to help you with the instalation of it. However i wouldent recomend overclocking as with my experiance the system became unstable and had bluescreens this could be due to my lack of experiance with overclocking but from my experiance overclocking wansnt needed and the system is perfectly stable at defualt clocks. assides that it is a brilliant pc and can run anything you throw at it and with the help of geforce experiance it optimises compatible games for optinum performance.