Quote:
Could I use an empeg player with an old 3.5" harddisk as a receiver at home...

You'd need to organise a converter from 44-pin IDE to 40-pin, plus get 5V and 12V supply from somewhere.

Quote:
How large would this harddisk have to be?

About 100Mb should do. Perhaps you could lash something up with a CF card?

Peter