How do I upgrade the hardrive?

atm I cant install the shivering isles or kotn disc, It says I need a hardrive..

You need to buy a new HDD. http://www.xbox.com/en-US/Xbox360/Accessories/HardDrives/250BGHDD

You buy one of http://www.xbox.com/en-US/Xbox360/Accessories/HardDrives/Home, or you use a HDD from an older Xbox 360. If you go with the latter then you'll have to remove the gray enclosure and then it'll fit into the 360 S's HDD bay. It'll also need something to support the weight of the HDD.

I'm currently using a 20GB from my original 360 in my 4GB S with a chunk of foam supporting it and it works just fine.

That question have you already asked http://www.gamesas.com/index.php?/topic/1142379-oblivion-goty-360-4gb-cant-install-expansions/. Please use that instead.

One topic is sufficient thanks.

http://www.gamesas.com/index.php?/topic/1142379-oblivion-goty-360-4gb-cant-install-expansions/