is it ok to overlock cpu and video and gfx cards?
It really depends on what you are overclocking? In theory, its not safe to do either, but if you have a decent CPU and GPU, overclocking can definitely be feasible. It is said that doing such will degrade your components, but that's really only true if the component came from the manufacturer already overclocked, or the parts are not of the highest grade.
The other worry is if you have enough cooling for the overclock. On AMDs, the stock fan will usually cool it enough to overclock the CPU 3-400MHz. GPUs on the other hand are questionable. GPUs are very very fragile, more so than CPUs, and should be overclocked with high caution. Depending on the fan that the manufacturer put on the card, and the airflow through your system, determines if overclocking is even an option.
So, in summary, it is fine to overclock either of them, as long as you know what you are doing, otherwise you void the warranty they so carefully worded.
arrogance breeds ignorance
Screaming Electron, Full of BSD Goodness