Arduino not detected I took an Arduino from a friend yesterday but when I connect it to the laptop there is no light blinking from the Arduino and the laptop doesn't detect any device.

Is there a problem with the Arduino or is there a possibility that the USB has problems?
Are you sure your laptop doesn't detect any device? It is possible that you need to install right driver for your arduino. The problem could be with:


Cable: Try to replace it with a working cable
Drivers Issue: You need to install driver for your Arduino. Generally, your laptop will issue warnings if it didn't find any appropriate driver for it.
USB-To-UART Bridge: This is an IC in arduino board. It needs to be working for laptop to detect your board. 
Microcontroller: Since, you told us that your board is blinking, then microcontroller will be working for sure.


Can you see any part getting hotter? Have you tried with other laptop and cable?