please help me to buy portable hdd

The WD Passports are really good, I've had one for a little under a year and it has worked w/o a hitch, I use it to store music and photos, and I listen to my music ALOT! I also have moved it around a ton. My only complain is that if it hasn't been used for a while it takes it about a second to spool up. But it doesn't need an external power supply, it gets everything it needs from the USB cable. Speaking of which, it's a little on the short side, but to me that doesn't matter. It's a standard USB cable so you can just buy a longer one. I highly recommend these. But they don't have an eSATA so if you need an eSATA then this isn't for you.

Hope this helps.