>>>Hi,
>>>my old disk drive in my USB to SATA 3.5" Hard Drive enclosure died so I bought a new one (2TB) and plugged it in. However, when I power the enclosure on and plug it into my USB port, nothing happens. Even if the disk has not yet been formatted, shouldn't the PC recognise it as a new drive? Or maybe my enclosure has died too?
>>Any signs of powering up (e.g. LED indicator, noise of harddisk spinning up)? If not, you could check with multimeter to see if the power adaptor is putting out enough juice. Also sniff near the circuit board in the enclosure to see if you have the telltale "fried component" smell. Another potential problem I've seen is sometimes the interface can't handle drives above a certain size.
>
>I've recently bought a neat little enclosure which didn't have its own power - it was powered via USB. Of which it had two, i.e. it would plug into two slots, daisy-chained. Didn't quite get the logic behind that until someone explained that one USB slot may not supply enough juice for the drive, but two would.

USB3 can help with that: https://en.wikipedia.org/wiki/USB_3.0#Power_and_charging

Still, it's pretty impressive that 2.5" mechanical drives and external enclosures/USB-to-SATA bridges can run on a total power budget of a few watts.