Hey.
-monitor displays no signal = monitor works, but no signal.
-Keyboard is not working.
-I see that you are having the problem with more than one peripheral. the reason should be from your central unit.
-Does your pc make strange voices when booting up ? does it make "bip" sounds random times ?
-If not, did you open your case before ? did you try to cool the motherboard with external fan ? touched it ? tried to clean it ? ..
-I believe you are connected to the internet, if you have a modem, does it disconnects randomly sometimes ?
-did you try to plug usb stuff and didn't work ?
-does the mouse act weird sometimes ?
-are all the fans in your pc working ?
-Do you feel any decrease in your pc performances (or felt, before the monitor stoped working) ?
-Does your pc overheats ?
-Do you get random shutdowns/reoots when your pc is on ?