Hi, there.
I have 2 extra hard drives and want to use them.
But I don't really like to open the tower case in order to connect them.

Is there any way that I can buy stuffs like some kind of cords...?
So I can plug "it" to the hard drive and plug to the computer without having to open the case?

Please be a bit specific.
Thanks.

Yes you can!!!

You would need to buy a hard drive enclosure to install your drive in. Then you plug it to your PC via USB. It is preferable if you have USB 2.0 for better data trandfer rate.

You can find plenty of enclosures here http://www.tigerdirect.com/applications/Category/category_slc.asp?CatId=1204

Just make sure you choose a 3.5" enclosure for desktop hard drives. 2.5" enclosures are for laptop hard drives.