Quite Pc How Can I Fix My PC, Which Is Quite New, And Won't Start Up Properly.?

How can I fix my PC, which is quite new, and won't start up properly.? - quite pc

On / off switch does not shut down, and the team is in a constant cycle (when it come unplugged) fans for 10 or 15 seconds, cut a few seconds, then repeat. You do not have enough time for everything that is displayed on the monitor. I am desperate. Any idea please?

This is an HP with XP Home.