PC starts but does not show signs of life

[emilp89]

Its my cousins pc, so I don't have a quick access to it. I ran out of ideas what to do...

CPU fan works.
There are sounds coming from the hard drive, so it is working, but the red light on the case that shows hard drive activity doesn't blink.
No beeps, no nothing.
No activity on the monitor (as if the pc wasn't turned on, no signal....).
The keyboard doesn't get any power (caps lock and num lock don't light up)
Graphic card is integrated.
The pc is older, the only thing that is newer is the PSU (couple of months new).

Tried cleaning memory stick and using a different slot.
Tried pulling the battery out, only for a min though.

Any ideas what could be wrong ?
Thank you

Edit:
The HDD is ok, I checked.

 

[Spartans]

There are tons of things that can get wrong, I advice you to get your PC checked, it could be the hard disk is dead, maybe you have a virus, maybe the gpu is dead hence the monitor is off problem, that's why this can't be resolved over the internet.but I think it's the motherboard, that is gone because every I/O doesn't work.