Why Is My Computer Running Slow

I’m currently running Windows 7. I’ve ran ALOT of anti spyware programs, antivirus and everything else. It just keeps happening. It usually goes in this order:
1) Internet cuts off (I have a laptop and yes, it detects other signals but when cut off, it won’t detect anything.)
2) two to five seconds later, the screen will go black (sometimes).

Any help would be nice.

I have a hardware issue making my computer load/run much slower. Is it more likely Graphics card, hard drive, or other issue?

Thanks!