Have you ever seen a message like this when you tried to upload a sketch on your Arduino board? if yes then you have got the same problem that I had but luckily I have found the solution after few painful hours of finding out the problem and solve it.
Why do I see "serial port com3 not found"?
Well, when this happened to me I tried to look for the cause of the problem, I found out that I didn't have USB2.0-Serial driver for my PC as you can the screen short below.
Where can I find "USB2.0-Serial" driver?
Go to this page (http://www.driverscape.com/download/usb2.0-serial) and download which ever folder is appropriate for your PC, after downloading the folder unzip it and the go to your Device Manager and update your driver make sure after clicking on the update drive button locate the right path to the folder that you download the above site, once you have successfully update the driver you will see your USB port like the image below.
That's it, now you can upload your sketch and enjoy!!! :)