Desperately need help- Lost !

I am a newbie at this so be patient. A friend used my computer and it looked liked he dwnloaded a lot of adult ent. (don't know if that matters) the next day i physically logged off and turned off my cmptr. About 6 hrs later tried to restart and I got Windows XP on screen with scrolling on bar below then I get a black screen w/ "DPMS Standby" in a small blue screen then seconds later I get "DPMS OFF MODE" then a blank screen w/ only my arrow cursor. Nothing. This will repeat evry few minutes or so. Have no idea what to do how to get anywhere.... totally lost and no one seems to have dealt w/ this before. Any suggestions?
Thanks