I am not a computer expert by any means. I actually use Macs so I don't have to really know anything technical and can still get my job done. I do know that low USB power would be a definite culprit as Rishma said, the pumps do not need to be connected. As far as setting the Com port, I believe this is in the my computer/settings header, we have a computer here with Windows we use for UPS shipping and I will try to figure it out later today. In March a new Windows program and a Mac version will be available which should solve most of these issues.