Only had desktop for a week now, bought second hand for my boys bedroom, but now again keep getting this message coming up on screen. When this happens i have to turn the tower off, then on again, is this a big problem to cure or something simple i could sort, thanks.
the fact that it's intermittent is a concern, that would indicate that either the hard drive or the controller is about to fail.
if it's the hard drive then a new hard drive is fairly cheap but you would need to reinstall all software again, if it's the controller then it's going to need a new motherboard. (the drive is more likely)
You will have to check that the hardrives power cable and data cable are connected properly, failing that maybe the hard drive is about to fail.
I had this problem on my girlfrinds PC and it was a loose DC connector to the drive.
On another PC of mine it occasionally did this but also powered down at random and eventually gave up booting all together.
Just take the side off and check that the cables are in right.