I Question about adding a harddrive to my mac

I just got one of the new imacs and i love it but i need more space on my hard drive. i was wondering if i could get an external hard drive and use like the one inside my computer like installing things in it stuff like that. if so what must i do???

If you were wondering about adding an external hard drive take a look at this one.

http://www.wdc.com/en/products/Products.asp?DriveID=232

its cool

its cool but can i connect it and use it like the one thats in my computer???

It connects with a usb cable. Its not as fast as your internal drive but if your using it for storage it will be plenty fast.

As long as you pickup a desktop external HD and not a laptop external drive, it will be the same hard drive found in your iMac. It's the same 3.5" HD drive, just in a sleek case with the USB or Firewire ports in the back.
The main difference in a desktop and laptop external is physical size. Well, laptop drives are slower and more expensive. Most all externals are designed for desktops because they also work with laptop, just the laptop versions are more portable.
The WD drive in the in the previous post is good. I have an upgraded version of that drive. It came with Firewire 400 and 800 ports. It's more expensive but firewire is faster than USB 2.0.
Hope this helps. (My advise really is to pickup a firewire drive) I would try and find one with a fan as well. It's louder but cooler.
Try tigerdirect.com. I bought a 250GB HD meant for desktop computers and bought a case for $75 total. My WD HD was $150 for a same size drive.
Peace,
Bryan

I'm in the same boat, I was debating whether to replace the Internal Drive and say good bye to my warranty but like bryphotoguy has said, just pick up an External.

I'm going for that Western Digital 500GB Version similar, if not the same as the one posted above.