Hi i am gonna buy a laptop that came with a 200G HDD at 4200RPM. it sound like it a bite slow. But i wanna know if it gonna make a big difference between this HDD or 120G at 5400RPM. I gonna use my laptop for processing photo, vidéo, playing game like Half-Life 2, Company of Heroes, etc..
There is only one reason to have a 4200 RPM hard drive whatsoever in a laptop. The reason is that you need every ounce of battery life you can squeeze out of your laptop. Otherwise, prepare for slow computer torture if you get a 4200 RPM hard drive. You will become miserable with it because 4200 RPM is extremely slow. I am speaking from personal experience here. Replacing my old 4200 RPM hard drive with a 5400 RPM hard drive was a great boost in speed for my old Inspiron 8000, which was built in 2001. For the applications you listed, you want nothing less than 7200 RPM in your laptop. Game loading times, photo editing, and video editing are greatly influenced by the hard drive speed. For basic office applications, 4200RPM will do, but I would recommend 5400RPM. Gaming, photo processing, and video processing demand at least 7200 RPM because those applications are hard disk bound at times. You will loathe any 4200 RPM drive that you get unless you primarily run CPU bound applications all the time that do not use the hard drive much. Only gaming fits that description, and if you game with a 4200 RPM hard drive, prepare for long load times.
Laptop HDD are slowe than Desktop HDD at the same RPM speed due to the smaller platter size. Hence a 4200RPM laptop drive is extremely slow.
Go for Either a 7200RPM drive or a 5400Drive w/ Perpendicular Recording. Perpendicular recording technology improves performance slightly making them faster than normal 5400RPM drives. Unfortunately there are not any 7200RPM PPR drives as of yet.
One thing that is constantly over looked is energy consumption. It a myth that 4200 or 5400 rpm drives saves you battery life. In realty you are waiting twice as long on a 5400rpm as a 7200rpm drive. The power draw is ~10% more, for a 80% increase in usage/performance.