It seems like almost all download sites, even the much loved Sourceforge, are including Adware with their installation software. In many cases these extra toolbars etc. are often in plain sight as you try to quickly push the Next button on each new screen.
Unfortunately, you now have to carefully look at each screen as if it’s a new legal document. If you just blithely keep clicking and accepting the defaults you can easily install a lot of crapware.
Ninite is the only site I know of that has resisted this temptation and seems to be free of any Adware.
Another solution might be the program Unchecky.
As you install a program you want and come to all those Extra adware installs, Unchecky automatically unchecks the install box. Here’s the video below.
NOTE – if you look at the 2nd video, you can see that Unchecky doesn’t ALWAYS work – BE CAREFUL – even with Unchecky.