hard drive 2.5" and 3.5"

[laoli]

you may know i am looking for a use hard drive (IDE). but i noted that there were tow kinds of hard drive, 2.5" and 3.5" in the ads. what size i should use?

 

[Rabbit]

好象机器里用的都是3寸的，笔记本用2寸的

 

[大熊猫]

台式机用3。5寸。