Cloud mass storage for LAN via Ethernet and USB shield

Hi everyone,

I have an Arduino Duemilanove board, and I have ordered Arduino Ethernet shield with micro SD card slot.
My intentions were to build a web server.
Then I realized, I have a (not old but not new) external Hard drive, which can be connected to PC via USB2.0.

My suggestion for the project

Arduino + Arduino Ethernet shield + Arduino USB2.0 shield + external HD = sort of a homemade cloud service for my local LAN or maybe it could be reached remotely.

I have searched the web but I haven’t found something similar. Do you think this could be built? Or do you know about a similar project. Maybe I have used incorrect keywords…? ?

Thanks for your suggestions and replies in advance.