If you no longer need a program on your computer, or if it is conflicting with other programs on your system, it's a good idea to uninstall it. Most of the time, the program's uninstaller will be adequate for this. You can find that by looking for the installer file, and then selecting "uninstall." This should remove all of the files associated with that program. There may be many other programs that wound up getting installed on your system that you're not even thinking about, and are just taking up space or resources. Here are a couple of tools to help you find and get rid of unnecessary applications on your computer:
On PC, check out ShouldIRemoveIt.com. This is a free Windows application that will help you decide whether or not you should remove a certain program. It scans your computer for all of its installed programs and leverages the wisdom of the crowd to determine which apps you really should uninstall. This will also remove adware, bloatware, toolbars, and other junk.
On the Mac, check out CleanMyMac.com. This finds the junk that got installed on your Mac and offers one-click cleaning. It also gets rid of the all the leftover files from uninstalled applications, and removes extra add-ons.