Hi [NAME] welcome to this free user-to-user Alienware laptop discussion forum.  Please run windows Reliability Monitor and wait for event timeline to be created. Look at events during every start-up for source of problem and Microsoft error code. How to use Windows Reliability Monitor to identify software issues | Dell US.   Please click on Product Support to identify system Model and Revision number, example x17 R2. Open Diagnostics tab and run the 40 minutes Full Test to thoroughly analyse your PC and detect any hardware problems. 
When I start the machine, the led and fan work normally but when I get to the screen, it hangs (maybe after a few minutes).The Caps Lock button does not work.I downgraded Bios to 1.8 and reinstalled win 10 but it still has that problem.I have powered it off and then restarted it many times but can't use it, sometimes the led is on and the fan runs but the screen goes black or the machine turns off by itself.
What causes the computer to hang on startup?