|Wherever possible go to the official website for everything you download and be careful that they have not used a crude disguise in their web address.|
Alternatively, when applicable, use a well known safe website such as FileHippo. They are trusted (which has led other websites to use filehippo in their name). It's a hornets nest out there these days, so always tread carefully, especially when downloading things to do with computers. The days of only getting unwanted stuff from just hackers, torrents and porn websites are over.
Another good program to run is ADWCleaner (small, fast and free):
Use the blue "download now" button near top right. Save the file then double click the saved file to run it (there is no install). Use the Scan followed by the Clean, although you can select what it removes if you wish. What it finds is useless or dangerous toolbars and other goodies. It updates frequently - you just download a new file.
This and MalwareBytes (already given) are good programs to have on board - they find the majority of nasties.
Always pop back and let us know the outcome - thanks