Backside plug-ins won't work

[valefar]

I got a little prob and i'd be glad you could solve it asap

i've been away from my parent's home for few months and my pc (asus i7 delux, which i bought last year) stayed there, useless and shut off.
Now, when i'm trying to turn it on, it goes all well, yet the monitor, keyboard, usb connection, and basically, any plug from its backside won't work.
When i tried to connect something to the usb connection from the front, it worked well. the dvd-rom works plainly clear too.
I open the pc and saw no unplugged wires.

What could make such a problem? power maybe?
dusting it was my first action, so i couldn't be it.

 

[raybay]

Have you run some good scans for infestations... Windows Security Essentials, Avira Antivir, Malware Bytes, and SuperAntispyware, to be sure it is not just a bunch of infestations?