Computer can no longer see Arduino; possibly burned out?
It might be possible that you fried the fuse or the regulator on it. To verify that you can use a multimeter. There is a regulator which looks like this:



You can see if the pins are short(which means it might be busted). 
You should never power a servo as mentioned above by Chris, as it can draw too much current. 
If the regulator is fried, you should give it a shot to replace it, instead of spending money for another one. 
ALso try connecting it to another laptop to see if it is detectable.