Side Effects of Wrong Voltage on Device

I have an odd scenario. I had a 5v 22 LED DotStar string attached to an Arduino Leonardo++ coected to my Acer r3 laptop via USB. One of my colleagues attached 12v to the LED string, causing it, the Arduino, and my laptop to stop working. Acer customer support instructed me to insert a small pin in the reset hole in the bottom of the laptop, which allowed it to boot properly, etc. but my inteet seems to be ruing slowly/hanging on all networks. Here's my question:

What other issues/problems might have been created by this?