I bought the RAMPS and Arduino Mega 2560 and 5 stepper drivers for my prusa mendel. I plugged in everything to the pc and everything was working perfectly. I installed all my arduino drivers easily. I used a 350w psu, but had some problems as 2 motors didn't work together so the arduino turned off when two drivers were plugged in. but still i could use a single driver. Then at my friends place when I plugged the psu to the mains and turned everything on, 1 of the stepper drivers started smoking from the chip attached to it and got fried. I think it was due to too much voltage. After a while removing the burnt driver when I connected my Arduino to the pc,(no RAMPS attached) the pc did not find its hardware. Only this 1 light stays on and nothing happens. I don't see that there is any physical damage to the board.. but there might be .. I am not sure what to do now.. I want to know if I can check weather the board is still working and how can I connect it to the pc? please help me 
Sounds like the stepper driver let the high voltage back onto its inputs when
it died. That RAMPS board doesn't appear to have any protection on the logic
inputs to the stepper drivers.
What board is it?
Which stepper drivers?
What voltages - just 5 and 12 from the 4-pin plug?
Its a RAMPS 1.4 board
The stepper drivers are standard a4988 stepper drivers
The Arduino is a clone
I just plugged in the 5volt pins with a 305Watt psu connected to mains.The psu has
+12VA=18.0A,
+12VB=18.0A,
+5V=22.0A,
-12V=1.0A,
+3.3V=17.0A,
+5VSB=4.0A outputs. I connected the 12volt 18A output to the 5volt input in the RAMPS
