This is where the program stops responding. You have seen those messages that says the program encountered an error, or is not responding. You can get out of this by pressing the ctrl-alt-delete at the same time, and close the program.If you have experienced any of these, windows registry repair software will find these errors, and fix them. The reason these errors happen is because of installing and uninstalling software. Also, if you have downloaded anything such as music on the internet, you will have these problems. The programs, when installed or uninstalled, will change your registry files. The can remove registry files, or just change them. Once this happens, if a program is looking for a registry file to get started, and it is not there, the computer will just freeze. In other words, this program will not work. Fixing the registry files will prevent these types of errors.