I have found out the answer to my own question. The error has been fixed by
installing Client for Microsoft Networks under my dialup properties,
although I don't actually need to use it to establish a connection.

"Daz" wrote in message
news:%23QBcbDcpGHA.3324@TK2MSFTNGP05.phx.gbl...
>I am running WinXP, Home, SP2 with all of the latest critical updates. I
>connect to the internet using an adsl modem and am not connected to any
>other network.
>
> During bootup, Event Viewer shows an error which states;
>
> "The IPSEC Services terminated with the error: The authentication service
> is unknown."
>
> If I try to manually start the IPSEC Services from Services I get the
> error;
>
> "Count not start the IPSEC Services service on Local Computer. Error 1747:
> The authentication service is unknown."
>
> Can anyone tell me why this is happening and if it needs to be fixed.
>
>