How can I upgrade my xbmc from ver 12.01 to ver 14.0 on my window laptop please?
If you have to ask its probably not for you... Its alpha software that *will* have bugs.
It might work from two versions away, but I would recommend going 12 to 13 to 14, since we don't normally test the upgrade progress between more than one version.
I would recommend to make a new installation.
Version 14 has not been released as stable yet. I would not recommend the upgrade process from 12 to 14 right now.
Go with 13.1 release. Wait on 14 for the stable release as others have recommended.