I had exactly the same problem, though I bought a win7 machine already with Start 10 Software, is it possible to transfer this software to my computer?
If you already purchased Start10, you can use the link I provided above and deactivate on old activation and reactivate on your other computer. If not, and the software came with the computer, than you need to talk to that computer seller on possibility to transfer those account to you. And you will need to raise a support ticket using the link below.
https://stardock.atlassian.net/servicedesk/customer/portal/4
Thank you,
Basj,
Stardock Community Assistant