I bought a pre-paid Sim-Card in November 2012 for use during my holidays in the USA. There was very little credit left on it. Can I reactivate this Sim-Card now as I'm heading over on holidays again or I am better just to buy a new one?
You'd be better off just getting a new one. Assuming there's been no use on that SIM for over a year, the card has most likely entered "terminated" status, meaning we would not be able to re-activate it.