The new machine boots up much more quickly than the old one - always handy for Windows, that - and is noticeably faster. The case is easier to put on and get off. The annoying high-pitched squealing noise present on the old machine has gone (can I hear a quieter, higher-pitched one, though?) but there is a very large fan indeed attached to the Duron which is rather loud - probably too loud to sleep through, I fear.
I haven't given the machine much of a test yet and I am sure that the machine will slow back right down once I load it up with