I bought my computer second hand, I'm not really too sure what it is server wise or anything like sorry. I have never had a problem with it until now! I was redecorating my flat so boxed up the pc and put it away, I have now put it all back together and all that keeps coming up on the monitor is no signal! When you turn the pc on you can hear it whiring as if it's loaing up etc, just nothing seems to be coming through to the monitor! Do you have any ideas what this could be?

Most likely some cables are loose. Check the cables.

What is the make & model of the computer?

Are you familiar with opening it up?

I would remove & reseat everything. CPU; RAM; Video Card; IDE cables; etc.

Quite possibly the moving moved something.

Do you have LED's on the case? Like: Green | Red | Amber ?

If so is the red light on?

Also: any BEEP sounds from the case?