My computer was reset and I've gone for the smog check twice but each time I am told to drive it more so the computer runs though all of the error codes.

My question is, how many miles do I need to drive?

 

50-2000. I've had the readiness monitors clear within those intervals. Harbor Freight sells a small red code reader that says "OBDII-CAN" or something like that that shows readiness monitors. Buy that and monitor after each drive. Or is you have a OBDII equipped D1/P38/D2 get an Ultragauge with readiness monitors and you can monitor your engine temps.