Does a USB hard drive of, say, 200 GB exist that you can just plug into your USB port and off you go? I guess I'm talking about Portable Hard Drives, aren't I? Do they always need a power supply and connection to the computer itself, or can you just 'plug & play'? If so, can anyone recommend any particular make? Thanks in advance, John.

I'm not aware of any 200GB USB HDDs that don't require a power supply but I'm sure that they exist for use with a laptop when AC power is not present. http://www.google.com/search?hl=en&rls=GGLD,GGLD:2005-01,GGLD:en&q=usb+HDDs+that+don%27t+need+ac+power&spell=1

John, Portable USB drives of 2.5" are widely available running upto 100 GB - it's possible there are others, however I haven't seen any. These are small enough to fit in a jacket pocket and do not require an external power supply, running off the USB 2.0 port itself. I have a 200GB Seagate HDD which does use a power supply. Not sure what you mean by "Plug and Play". You need to have an internal Hard Drive with an OS set up to run these. Then you need a driver disc to install the hard drive hardware for recognition by your computer. Seagate, Fujitsu, Samsung, Lacie, Western Digital, Maxxtor all make hard drives of 200GB+. For convenience, get one fitted into a hard drive case with a one touch button back-up. Depending on where you live, you can mix and match hard drives with cases. Good luck.

Thanks to you both for your help. I get the picture - basically (with the current technology) up to about 100 GB, you can get the small pocket-sized ones. Then you're looking at a USB external hard drive, which still needs a mains supply. That's nice & clear! Thanks for the input, John.