If you've reached your max number of activations, I think Vegas gives you the option of deactivating other machines, but if not you can log into your account at magix's website and do it from there.
Hi FrOsty, thanks for replying. No I have only installed it on one pc so far, an older X79 system, and I want to move it to my X99 10 core system. I want to keep as many activations available as possible, for the future. I'll check my account like you advised.