Ok sorry if this has been covered but just don't have a clue as to what the fault is apart from the symptoms.

I have a pc with 4gig ram q6600 cpu and I have installed Ubuntu 12.04 and then installed KDE I have added several applications including Compiz and cairo-dock the reason I have brought them up is that I have seen lots of problems with them on forums.

The machine for no reason will just Lock up and the only way is to power down and Power up the machine.

I am a windows user that's moved over to linux so I am new at this, I could do with some advice or help on what I can do to diagnose the problem.

any help would be great