Yea, you will need to follow the directions for Refund, on this Policy page to get the refund, if you already owned 3.303.
http://www.mtu.com/support/returns.htm
You will need to email sandy at mtu.com with the order number and tell her that you already were entitled to this, and to please credit your account.
Anyone can purchase the upgrades, as beavis stated did you look to see if you had the download link in your order, before just purchasing?
Your discs dragging problem, is going to be related to something in your computer. The only real way to probably get rid of this problem is to format your system and reload Windows and all the drivers. This will bring to a brand new system. Then it will most likely work.