I upgraded from the trial version but the installation doesn't allow me to get past the initial serial number window. Once I fill in my serial number it loops ack to the same window/dialog box. I tried to get past it and it loops again.
Inevitable question, I suppose: which program? You chose ACID Music Studio as your product, is this what you have installed? If so, is the serial number definitely for that app, or, perhaps, for another product from the ACID stable? If you check the confirmation email received when you bought the product, what does it show as the product you actually bought?
Sorry if this is not the case for you but serial numbers being rejected is often caused by them being for a "different" app, or even a different version of the correct app to the one the user is trying to register.