Don't worry too much about this, I have often seen smartscreen prompts saying this sort of thing. Make sure to scan the files you download with an anti-virus and a second opinion antimalware program, make sure to use safe sources for downloading them and check the files' digital signatures are valid(some programs from small developers might not have one at all but those from larger organisations and companies should). You could also upload the files you download to virustotal to check whether other antivirus programs than your own find anything nasty in them. When you try to run a downloaded program file if the smartscreen prompt appears follow the option to "run the file anyway" (it might be named slightly differently to that).Smart screen is a separate layer of defence to UAC, leave UAC enabled as UAC gives you an extra warning before running the file, just so you don't run any exe files by accident.
The order for what you do, and what you observe, should be this:
1)you download a file and choose which folder to save it to
2)you scan it with your antivirus
3)you scan it with an on-demand antimalware program (like malwarebytes free)
4)you right click on it and look at it's properties, see if the digital signature, the publisher and such seem right
5)upload to virustotal for further checking of whether the program is safe
6)if it passes all those tests then you run it
7)double click on the file in file explorer
8)the smart screen prompt appears, if ti says something along the lines of "this file is known to be malicious" then don't let the file run any further, if it says "Windows Smart Screen Can't Be Reached Right Now" then follow the option to proceed anyway, in some cases no smartscreen prompt will appear at all.
9)now the UAC prompt appears, check it quickly to make sure it sounds right for the file you are trying to run, does the name match? is the publisher who you expect it to be? is the signature valid(it will say if it is not)?
10)If everything seems ok at the UAC prompt then click the option to continue and run the program.
I am assuming this smart screen stuff only happens when you download programs (exe files), it certainly shouldn't happen for other (image,document,video,audio,archive) file types.
Edited by rp88, 16 April 2015 - 12:15 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB