^ This is Not a USB2 vs USB3 throughput question. The drive is backwards compatable and should have worked equally as well as his old usb2 drive. The problem is either A) the quality with the HDD, or B) a power problem
Most look at throughput when talking about backwards compatable. With Usb External drives you must also look at power. Some HDDs draw more power than can be supplied by a single usb2 port.
1) When plugging the External drive in are You:
.. A) Plugging into only one usb port (Power limited to devices that draw < 2.5 W)
.. B) Plugging into two usb ports (allows more current to device)
.. C) using a usb 5V/2V AC power adaptor (For external HDD this is what I normally use). If no powr connector on enclusure Us a powered usb Hub.
** Not sure but I thought they increased the allowable current (power) for USB 3. if that's the case then would have to look at the max Current drawn by the toshibia HDD.
While the drive is 100% backwards compatable - that is for throughput and does NOT address the power requirements (However They should clarify, need more power than single USB2 port can provide.). Also intial power on for the Xternal will be anywheres from 1.5 to 3 times higher than nominal current.
2) does your laptop have a expresscard slot, if so:
http://www.newegg.com/Product/Product.aspx?Item=N82E16839328044
Added:
Just took a look at newegg - None of the 1 TB 2 1/2 Form factor drives have a "good" 1/2 (Bad) egg ratings. And None of them listed Power consumption.