I too have that problem with Vista Home Premium and flash player.
I have done everything that Adobe suggest to do on their support website and still can't get it to install right.
I have done all the steps that you have and just can't get it to work. It says it downloaded OK, but it didn't.
Can't run flash player with Windows Vista Home Premium. Adobe download site says its installed, is is not. I have tried everything re-downloading,nope, re-installing nope, disabling pop-up stopper, Norton Interent Security and Virus, nope, system restore no go even in safe mode. I'm out of ideas need help if you can, thanks.