Windows 7 has a tool which lists almost all the installed applications on your computer, which is a great way to add/remove/modify the software. To load this "Add or Remove Programs" list, type appwiz.cpl in to the start menu search or run box and press enter:
Clicking on any software item in the list will bring up a choice of options on the blue toolbar. Usually these are Uninstall, Change or Repair.
Uninstall will remove the software from your computer, including data files, registry entries and start menu/desktop shortcuts.
Modify allows you to change the software install, for example adding or removing components in an office suite.
Repair can be performed if the software is missing files or behaving incorrectly. This will attempt to replace corrupt or changed files with the originals.
Once you have selected the operation to perform, the installation wizard will guide you through the rest of the process. This can vary depending on each application, but it should be straight-forward to follow.