There are seven Run keys in the registry that cause programs to be run
Keys 1 through 7 apply to Windows 95, Windows 98, Windows 98 Second Edition, and Windows Millennium Edition (Me).
Keys 1 through 4 also apply to Windows NT 4.0 and Windows 2000.
For Windows 98, Windows 98 Second Edition, Windows Me, Windows NT 4.0 SP3 or later, and Windows 2000, an additional rule is available;
for keys 3 and 4, the value name can be prefixed with an asterisk to force the program to run even in Safe mode.
Keys 1 through 4 are run each time a new user logs in.
Keys 5 and 6 are run in the background when the logon dialog box first
appears, or at this stage of the boot process if there is no logon. These
keys are for background services such as remote registry service and are
run only once per boot.
Key 7 is run as part of Setup's first-boot activities, or after you use
the Add/Remove Programs Wizard.
Under each of these keys is a series of values. The values are used to
allow multiple subentries to exist without overwriting one another.
The data value for a value is a command line. By default, Run keys are
ignored in Safe mode. For keys 3 and 4, the value name can be prefixed with
an exclamation point to defer deletion of the value until after the
command has been completed.
For keys 3, 4, and 6, the value is deleted before the command line is
run unless overridden as noted above. As a result, if a RunOnce operation
fails to run properly, the component that failed will not be asked to run
again the next time you start the computer.
Key 7 is used only by Setup. This key displays the progress dialog box as
the keys are run one at a time. For key 7, the name of the value is the
name that is displayed in the dialog box.