If none of those work, you will want to try to isolate the issue by replacing things: try a different computer on the same arduino, try a different arduino on the same computer, and try using a different USB cable. Disconnect everything to Arduino, Plug in your Arduino to your computer - check for the Serial port, Check for your Arduino Model, select programmer as USBasp, open up BLink sketch from Examples and HIT upload.
Make sure digital pins 0 and 1 do not have any parts connected, including any shields.Go back to Tools ► Serial Port ►, and see which port appeared that wasn't there before.Go to Tools ► Serial Port ► and see which ports are listed (e.g.One way to figure out which port it is on is by following these steps: Make sure you selected the right port in Tools ► Serial Port ►.The board should say what version it is on the microchip. If you are using the Duemilanove 328, select that instead of Duemilanove 128. Make sure you select the right board in Tools ► Board ►, e.g.Disconnect and reconnect the USB cable.Here are some easy things that can often fix this error: This is caused by a generic connection error between your computer and the Arduino, and can result from many different specific problems.