Halion3.5 and Cubase6?!

Greetings to you all,

I have a problem and I need help. I am in posesion of Cubase SL3 nad Halion3, and licences for them are on usb which is registrated several years ago. This year i have bought and Cubase6 and it’s licence is on another usb. Currently, on my computer C6 is installed, and everything works perfect. I wanted to install and h3, but a problem occured. When the instalation began, i received a message that it is not possible to install it ( i have made 2-3 attempts) I have turn on the key with licence for Halion3, thinking that this may have caused it, but nothinh has changed. Then, something confusing happened. I have downloaded update Halion 3.5 64 bit from Steinberg’s site (because I have win7 pro 64, but earlier I had XP pro 32). I have simply ran instalation and in a few seconds everything was completed. H3.5 works without demand to turn on usb, nor any code was requested. What happened? How is it possible that H3.5 (which is update) works without prior instalation of H3? And why it does not request any licence nor registration? Does this mean that I may install my old H3 on another computer and use usb key, considering the fact that H3.5 does not request key? I am quite confused with this situation. I hope for quick answer. Thank you in advance.