1. Yes, just stop using the license on your old pc and start using it on the new one, that's all. To make sure you can remove the "Registration key=" line from C:\Users\username\stereo_tool.ini (or just remove the whole file if you don't care about your settings).
2. Yes, by paying the difference in price. We don't have an automated way of doing that, so please send an email to firstname.lastname@example.org
. (Upgrading is only useful if you need Enterprise-specific features (watermarking, better password protecton) or if you're going to run multiple instances on the same system.)