Run and RunOnce Registry Keys
Run and RunOnce registry keys cause programs to run each time that a user logs on. The data value for a key is a command line no longer than 260 characters. Register programs to run by adding entries of the form description-string=commandline. You can write multiple entries under a key. If more than one program is registered under any particular key, the order in which those programs run is indeterminate.
The Windows registry includes the following four Run and RunOnce keys:
By default, the value of a RunOnce key is deleted before the command line is run. You can prefix a RunOnce value name with an exclamation point (!) to defer deletion of the value until after the command runs. Without the exclamation point prefix, if the RunOnce operation fails the associated program will not be asked to run the next time you start the computer.
By default, these keys are ignored when the computer is started in Safe Mode. The value name of RunOnce keys can be prefixed with an asterisk (*) to force the program to run even in Safe mode.
A program run from any of these keys should not write to the key during its execution because this will interfere with the execution of other programs registered under the key. Applications should use the RunOnce key only for transient conditions, such as to complete application setup. An application must not continually recreate entries under RunOnce because this will interfere with Windows Setup.