A second-hand PC already containing a fresh install of XP pro suffers from a 20 sec delay before dialling. Once the modem starts to dial everything seems normal.
I have come across a similar problem on Win98 which can be fixed by leaving only TCP/IP protocol (in Control_Panel/ Internet_Options/ Connections/ Settings/ Properties/ Server_Type) However I have been unable to find any XP settings which affect this unwanted delay.
There is no network connection and the Ethernet device is shown as disabled.
The modem log file extract below shows where the delay occurs: