Personally I don't own a system with over 160gb, I'm such a bargain bucket, my system has 75gb rofl, and my laptop is just a joke, someone took the 250/300gb HDD out before I bought it and shoved a 60gb in and took the 1gb memory to, left me with 1gb lol, cheeky, either way I got them down to 120£ for a decent laptop.
I think it's still a big beta, I'm sure they will shrink it and soon enough you'll have it on a usb stick.
I to had a laptop that wouldn't boot from USB, took me about 5 different flash sticks and a few different software to burn to usb, I'm sure you'll be able to do it if you really want to, just a pain in the butt.