You get Adobe flash from www.Adobe.com . On the Adobe (UK) site, the link is in the third block down on the right hand side of their homepage.
With regards to your other problem, since you posted in the Win 7 section of BC, I presume you are running Win 7 ! then I would suggest you use the 'Restore point' system and restore your computer to a time before you attempted this download. If you have never done it before, it is quite easy.
'Start' - 'Control panel' - 'Recovery' - 'Open System Restore' . There you will be presented with a list of available restore points. Just pick the last one before you attempted this download and carry on. this should restore your operating system to the condition it was in before things went wrong. Just one word of advice - back-up your own data before you start this process.