What is the difference between “manual” and “disabled” service in Windows?

Windows services seem to come in three start-up types:

• Automatic: seems to mean that it is started at bootup
• Manual: seems to mean that it is not started at bootup
• Disabled: also seems to mean that it is not started at bootup

What is the difference between the latter two?

Manual means that the service will start only when Windows or another service needs it, or if you invoke something to start the service. You can use the command net start servicename from the command line to enable a manual service. When you reboot, the service will again be off until you restart it.

Disabled, on the other hand, means that the service will stay off, regardless of whether you try to start it or not. Other services or applications which depend on the disabled service may fail.

See the MSFN discussion thread on Manual vs. Disabled for more info.

The only difference between manual and automatic is that in the case of automatic the operating system itself starts the service after boot up, whereas in the case of manual the service is only started when called upon by another service or program.

If you have no need of the service at all, you have to disable it. Telephony seems to be one of those services that always wants to start up even when you seemingly have nothing that uses it, and the system would always complain if you disabled it. They seem to have fixed that problem in Vista, and they may have fixed it XP/SP3.