Let me see if I have this right: The $29.99 upgrade to TI 10 offered on the web site can be installed even if a prior version is not installed on the hard disk, so long as you have a valid serial number from a prior version to input during the installation. The $19.99 upgrade many of us received via e-mail requires a prior version to already be installed on the hard disk. In other words, it can only be installed over a prior version. Correct? Presuming for the moment that I am correct, what is the logic behind this dual approach?