Can you Connect computer via usb port to stereo?

In most cases, no. A stereo will generally need a 3.5mm headphone jack, a 1/4" headphone jack, a SPDIF digital output, or an optical output.

However, some newer systems do have a way to be plugged in through USB, and you can also buy adapters that plug into a USB slot and provide a 3.5mm headphone jack for a speaker to plug into.