Have a look at the Asus eeePC - it's exceedingly small, looks cool, and it's dirt cheap (<£200). Obviously it's not a desktop replacement, but it does make a nice toy. I really like my 12" Powerbook - maybe have a look for a second hand one? Should be <£400 really. As for syncing, I use Microsoft Synctoy. Use it over the network, or whatever. You can't just share via USB, but you can with Firewire, obviously only if both computers have it. Yes. Not massively, but notebook hard drives are slower, and a few other reasons which escape me.