I own latest Vegas but also own Vegas 12 by sony. I installed it in copy of window enter the serial # and then get stuck at the registration window. how to bypass
Older versions of Vegas Pro than 14.0 are licensed under a system (as previously used by Sony) which permits use on multiple computers by one user; after an unspecified number of installations on different or updated PCs you may need to contact support to reset your "installation count"
The sentence highlighted in bold might be the problem. If it is, you'll need to contact MAGIX support to get the 'installation count' reset. There's a 'Contact Support' link at the bottom of this Support webpage.