Why won’t my laptop see my drive?
My laptop lacks an optical drive, Q so I bought an external USB drive to play DVDS and install older software. However, my laptop doesn’t always recognise this external drive. Weirdly, plugging the drive into another PC and then into the laptop sometimes overcomes the problem. However, this is far from convenient. Do you have any idea what might be causing this? I have no problems with my laptop recognising other USB devices. Jim Morris
A We suspect this comes down to power – or rather the lack of it. The bottom line is that not all USB ports are equal. A USB 2.0 socket, for example, should deliver up to 5V at 0.5A current, for 2.5W output, while USB 3.0 and later ports increase this to at least 5V/0.9A for around 4.5W output. But these are nominal outputs and, in reality, the level can vary a little.
You didn’t give us details about your laptop or USB drive. However, if the former supplies a tad less power than the ideal and (or) the latter requires too much power, it could lead to recognition refusals – simply because the drive isn’t receiving the power it needs to operate.
Evidently, your other computer has sufficient power to allow the drive to work. We’re not entirely sure why plugging it in to the first computer usually allows it to work in your laptop, but we’re guessing some tiny residual charge gives it the kick it needs.
So, is there a solution? Well, in the first instance, make sure your laptop is plugged in at and powered by the mains. Alternatively, or as well, try connecting the drive to different USB ports on your laptop. As noted, a USB 3.0 or later port should provide more power than the older USB 2.0 type. USB 3.0 ports often have blue plastic interiors, incidentally.
Finally, you could invest in a mainspowered USB hub. We cannot guarantee that this will fix the problem, but if lack of charge to the drive is the root cause, it should. The pictured RSHTECH model (around £24, www.snipca.com/41650), for example, delivers 5V/2A, so will provide 10W output: that should be enough to power an external DVD drive.