user253: Edit - Sorry it's a Micro not a Nano
I have a Micro board hooked up to an EasyDriver breakout using its 5V output to power the Micro. 
Today I plugged it in and instead of booting up like normal the power LEDs on the wall plug, the easy driver, and the Arduino started flashing. The Micro became very hot, but not hot enough to burn.
After that if I plug the Micro into the USB port it just rapidly blinks the pin 13 LED. The PC does not detect the device but it does receive power.
Holding or pushing the reset button doesn't seem to help at all. I've used different USB cables, and different ports on the PC as well to no effect.
Is this something it can recover from? Why did all the LEDs blink like that? 

user6936: I have had a similar problem, on a Pro Micro, and the PC, in the end, could not see it, and it would not show up in Device Manager. It was, to all intents and purposes, bricked. 

It could be just a question of timing the double resetting of the Micro correctly, in order to enter bootloader mode, see Pro Micro & Fio V3 Hookup Guide - Troubleshooting and FAQ - Reset to Bootloader:

While the Micro is in Bootloader mode, you should see it appear in Device Manager like so:

While it is temporarily in this bootloader mode, you should be able to upload a new sketch.

However, this did not work for me and I ended up having to burn the bootloader again, via ISP, using either a USBasp or an Arduino Uno configured as an ISP.
After a number of attempts the apparently bricked Pro Micro showed up again in Device Manager, and became fully functional:
 
After that, all that was required was to install the correct Windows drivers, to get rid of the yellow warning icon.  From Pro Micro & Fio V3 Hookup Guide – Installing: Windows, obtain the zip file Arduino_Boards-Master.zip. Then selecting the Pro Micro in Windows Device Manager, right click and “Update Driver Software”, following these instructions, from the link:

Unzip that zip file, and don’t forget where you’ve left its contents.
  In that zip file, you should find an INF file, which contains all the
  information Windows needs to install the Pro Micro’s driver. This
  sparkfun.inf will be found in Arduino_Boards-master → sparkfun → avr →
  signed_driver.

Once the driver was installed, then the Pro Micro should appear correctly in Device Manager

If you haven't already done so, add the following URL to the Board Manager line in the Preferences dialog in the Arduino IDE:
https://raw.githubusercontent.com/sparkfun/Arduino_Boards/master/IDE_Board_Manager/package_sparkfun_index.json

Then opening the “Board Manager…” in the Tools/Boards menu, search for the “SparkFun AVR Boards” package and install it. 

I have written two lengthy blogs about the whole experience:

The case of the broken Pro Micro
The case of the broken Pro Micro (reprise)


253: <p><em>Edit - Sorry it's a <strong>Micro</strong> not a Nano</em></p>

<p>I have a Micro board hooked up to an EasyDriver breakout using its 5V output to power the Micro. </p>

<p>Today I plugged it in and instead of booting up like normal the power LEDs on the wall plug, the easy driver, and the Arduino started flashing. The Micro became very hot, but not hot enough to burn.</p>

<p>After that if I plug the Micro into the USB port it just rapidly blinks the pin 13 LED. The PC does not detect the device but it does receive power.</p>

<p>Holding or pushing the reset button doesn't seem to help at all. I've used different USB cables, and different ports on the PC as well to no effect.</p>

<p>Is this something it can recover from? Why did all the LEDs blink like that? </p>
 6936: <p>I have had a similar problem, on a Pro Micro, and the PC, in the end, could not see it, and it would not show up in Device Manager. It was, to all intents and purposes, bricked. </p>

<hr>

<p>It could be just a question of timing the double resetting of the Micro correctly, in order to enter bootloader mode, see <a href="https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide/troubleshooting-and-faq" rel="nofollow noreferrer">Pro Micro &amp; Fio V3 Hookup Guide - Troubleshooting and FAQ - Reset to Bootloader</a>:</p>

<p><a href="https://i.stack.imgur.com/VBdHc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VBdHc.png" alt="Pro Micro and Fio v3 reset functionality. Press reset twice, quickly to enter bootloader mode"></a></p>

<p>While the Micro is in Bootloader mode, you should see it appear in Device Manager like so:</p>

<p><a href="https://i.stack.imgur.com/8bZ90.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8bZ90.png" alt="Pro Micro in bootloader mode - in Device Manager"></a></p>

<p>While it is temporarily in this bootloader mode, you should be able to upload a new sketch.</p>

<hr>

<p>However, this did not work for me and I ended up having to <a href="https://learn.sparkfun.com/tutorials/installing-an-arduino-bootloader" rel="nofollow noreferrer">burn the bootloader again</a>, via ISP, using either a USBasp or an Arduino Uno configured as an ISP.</p>

<p>After a number of attempts the apparently bricked Pro Micro showed up again in Device Manager, and became fully functional:</p>

<p><a href="https://i.stack.imgur.com/2wlLv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2wlLv.png" alt="Pro Micro with driver warning - in Device Manager"></a> </p>

<p>After that, all that was required was to install the correct Windows drivers, to get rid of the yellow warning icon.  From <a href="https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide/installing-windows" rel="nofollow noreferrer">Pro Micro &amp; Fio V3 Hookup Guide – Installing: Windows</a>, obtain the zip file <em>Arduino_Boards-Master.zip</em>. Then selecting the Pro Micro in Windows Device Manager, right click and “Update Driver Software”, following these instructions, from the link:</p>

<blockquote>
  <p>Unzip that zip file, and don’t forget where you’ve left its contents.
  In that zip file, you should find an INF file, which contains all the
  information Windows needs to install the Pro Micro’s driver. This
  sparkfun.inf will be found in Arduino_Boards-master → sparkfun → avr →
  signed_driver.</p>
</blockquote>

<p>Once the driver was installed, then the Pro Micro should appear correctly in Device Manager</p>

<p><a href="https://i.stack.imgur.com/kH4QO.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kH4QO.png" alt="Pro Micro - in Device Manager"></a></p>

<p>If you haven't already done so, add the following URL to the Board Manager line in the Preferences dialog in the Arduino IDE:</p>

<pre><code>https://raw.githubusercontent.com/sparkfun/Arduino_Boards/master/IDE_Board_Manager/package_sparkfun_index.json
</code></pre>

<p>Then opening the “Board Manager…” in the Tools/Boards menu, search for the “SparkFun AVR Boards” package and install it. </p>

<hr>

<p>I have written two lengthy blogs about the whole experience:</p>

<ul>
<li><a href="https://gr33nonline.wordpress.com/2015/08/05/the-case-of-the-broken-micro/" rel="nofollow noreferrer">The case of the broken Pro Micro</a></li>
<li><a href="https://gr33nonline.wordpress.com/2016/10/19/the-case-of-the-broken-pro-micro-reprise/" rel="nofollow noreferrer">The case of the broken Pro Micro (reprise)</a></li>
</ul>
