That is not entirely true. For a laptop, as long as you have USB ports you can merely attach an external hard drive.
Also, if your feeling adventurous, you can actually replace the hard drive in a laptop.
I had an old PIII Compaq laptop with a 30GB 5200 Rpm Hd in it (which was a defective design from day one and was replaced at least 3 times by my Dad - who offered it to me out of the trash).
I installed a newer Hitachi 60 Gb 7200 Rpm drive and a clean copy of Windows XP about 3 years ago. I dumped the entire Compaq software package that came with it) and I've been using it ever since. It's been as far as the Philippines (I was doing homework for an Solidworks class via email on vacation in 2007).
It taken a beating, too. Only one optical drive works sporadically and the usb ports are broken but its still good for web-surfing and I've got 2 other pc's ...