How can I fix my computer .. I use it everyday could it be over used ? When I went to turn it on .. It won't.?

My windows xp desktop system told me I had updates so I shut it down when I went to turn it on it went to a black screen with an underscore flashing in the top left corner I pressed (ctrl+alt+del) and it gave a whole bunch of computer language things I don't understand the. Went back when I tried it again it didn't work now it won't turn on what can I do to fix it if possible PLEASE! HELP!!