Adobe has not "officially" supported the plugin for Vista since version 10 of Flash because (I'd imagine) of the limited number of Windows users who still actually run it. I have a testing machine with Vista Ultimate and I run Flash Player 11 on it, but it ISN'T officially supported.
If you have a multicore processor, your "true" speed is the sum of each core (ex: a quad core 2.1ghz machine is actually 8.4gHz in bench testing for performance). In your case you have a 2.1gHz dual core, and the minimum required is a 1.9gHz dual, or a 2.33gHz single core P4 (3gHz P4 for some systems - based on the resolution stated above it looks like a laptop requirement).
Again I know from personal experience that FP 11 will run in Vista, but that is no guarantee that it will in ALL Vista systems. Given the extremely short run that Vista had before 7 replaced it, I doubt Adobe will officially support any future version either.
actually Flash Player versions 11.7 and 11.8 do support Windows Vista, Mike M.
so you are wrong with your assessment with Vista. see here for the requirements for Adobe Flash Player 11.x:
2.33GHz or faster x86-compatible processor, or Intel® Atom™ 1.6GHz or faster processor for netbooks
Microsoft® Windows® XP (32 bit), Windows Server 2008 (32 bit), Windows Vista® (32 bit), Windows 7 (32 bit and 64 bit), Windows 8 (32 bit and 64 bit), or Windows Server 2012 (64 bit)
Internet Explorer 7.0 or later, Mozilla Firefox 17 or later, Google Chrome, or Opera 11
512MB of RAM (1GB of RAM recommended for netbooks); 128MB of graphics memory
and Microsoft hasn't retired Vista support entirely until April 2017 as noted on one of their support pages on Windows Vista. and yes I still run Vista but at SP2 level and it's as stable as Win7 RTM. so current and future versions of Adobe Flash Player will support Windows Vista until Adobe changes their mind later on.
When I posted that repsonse, the page you linked to DID NOT have Vista listed as supported, because at that time, the decision to continue support for Vista had not been "officially" made and the LATEST version supported was 10.2. I received more than a couple messages from MVP members and employees alike asking me to "stop telling people they can install 11.7 on Vista just because you could. The official position is that it isn't supported." So I posted what was correct at the time. Being as that was four months ago, your reply would have been relevant then, but I don't suppose you bothered to look at the date before you posted.
I have Vista 64 bit Ultimate SP2 myself, for testing, with Flash Player 11.9, Adobe Reader 11.0.5, IE9, Firefox 25, Opera 17, Safari 5 and Chrome 30. I aslo run Office 2007 and Creative Suite 4, though they aren't "officially" supported anymore.