tried about 7 times, each time it tells me to turn off internet explorer (which i do), but upon trying to restart download, same error message. tried saving the download, closing everything, then installing & (surprise) same message. any thoughts? rapidly losing my cool
Wouldn't want you to throw a tantrum. You might give yourself apoplexy.
What's happening is that you have an antivirus app installed which includes a file scanner. When you attempt to run the Flash executable, it springs into action and begins scanning the file. This interferes with the installation to the point where it fails, usually at 50% like you say.
Do you have AVAST installed? If so, right click the orange Avast icon in systray and choose to disable all shields for one hour. Then run the installer again. If you have another AV, look for a menu which gives you the option to disable the shields temporarily.
Here are some example of incidents similar to your own which were fixed using this approach: