difference between 3.5 hdd and desktop hdd?

haiya guys! 'just wanna know if the 3.5 hdd can also be used on desktop computers? or is it for laptops only? but I know that the hdd for laptops are 2.5. plz correct me if im wrong.

Laptops mostly use 2.5 hdds, and desktop computers usually use 3.5 inch hdds. Usually you can't just take 3.5 and put in in a laptop, or take 2.5 and put it on desktop machine, but you can do this easily with a rack. Some external racks have USB support, and better ones can be used for both 3.5 and 2.5, so you can plug any hard drive in any computer. 2.5 hdd can be fitted in small inexpensive racks with USB support that cover the whole disc and then you can carry them in you pocket because it's not much bigger then pack of cigarettes (but you should be careful not to drop them).
Other then that - 2.5 are usually slower and more expensive, but they consume less power. 2.5 should also be more shock resistant, at least in theory.

You can get a laptop HDD convertor -> IDE for about £6 which is extremely useful for fixing laptop software problems. Or if you just have a spare LP-HDD around

I've plugged my laptop 2.5" hdd into a desktop before using an eSata cable and the generic power supply. As long as the plugs match (power+cable) up the only issue that you should be worried about is size.