Computer wont power up

hi I have a amacro with arctic cooling its got dvd drive but my problem is when I power it up it goes on to the windows xp screen and just stays there loading up for 5 mins then turns itself of and repeats its self time and time again ive looked inside the computer and all looks well even clean the fans and still nothing I even went out and got a knew windows xp dics and tried running that but when it gets to boot up from cd press any key my keyboard wont let me press eny thing and it just repeats it self I can get into bios and that all looks fine as well please help as im stumped please can someone get back to me asap as its the main computer for the house ive had to borrow a mates laptop to try and get some help thanks