If you're having trouble opening a file since you don't know what software to use, a good Googling will probably yield some answers. I previously had trouble opening ICA files and did a Google search on how to open it. There are a lot of websites that have an extensive database of the different file extensions and which software to use to open them.

Internet saves the day again. However, what will happen if you need to open a file and there's no internet connection anywhere? Say, you can't open something with the file extension WPS? Well, all you actually need is the Notepad on most Windows PC. You just open the unfamiliar file and somewhere in the document you'll find out what software that file has been created with.