Moniter screen stopped showing with hard drive.

Yesterday I was just doing random stuff, trying out fangames and what not. Then, all of a sudden, my moniter just shut off. I unplugged the cord for about a hour, and it still wasn't showing anything. When my mom got home, we tried using the moiter with my hard drive downstairs, and it worked somehow. Yet, we cant get any moniter to work with my mom's hard drive(I installed PSOBB and some stuff on her computer).

Does anyone know what my problem might be?