Vista x64 is unsupported and untested, however the installer shouldn't block you as far as I know. Can you tell me what the file name is that you are trying to install?
Unless you're using a 64 bit browser, you should be able to install the 32 bit version of Flash Player which you can find here.
Thanks for the swift response but I think that I figured it out and I have
installed successfully the latest ver of Flash. Thanks again!