Installing and downloading

Good day everyone..I just want to ask for help..I can't install and download software for some reasons in my laptop..whenever I try to install a software,it always prompts me to choose a program that I should open with even when it comes to software..I don't know what to do..My files are also the same..whenever I try to open a file it always ask me what program should I open it with.. Also, sometimes the download toolbar at the bottom of Internet explorer doesn't work..It's because of these problems that I can't install firefox and google chrome..help me please..