If you run on your computer, the application attacker, it is no longer your computer. Written on the one hand, all right. But it does not mean that you can not run anything at all. And in order to assist in the control of that run, for example, helps such a service as UAC Windows Vista. After all, in fact Windows Vista operating system by default is quite protected. But the application does not have the administrative rights in general very difficult to 'take' you have a computer. In fact, as soon as the application requires you have administrator privileges to harm – You and only you decide to press 'Yes' or enter the administrator password in window service UAC. And then the law provides a good example of a sandwich. No need to download software from unknown sources.