Sharepoint installation error

[David]

While installing Sharepoint using the STSwiz.exe I am
getting the following error:
"Sharepoint Team Services failed to provision Default Web
site.
You have entered incorrect database information.
The specified virtual server cannot be extended by
Sharepoint.
You can investigate the problem via "Microsoft Sharepoint
Administrator" in Adm Tools.
To fix the problem remove Sharepoint Team Services & try
the installation again"

The database information is correct. What is this problem
about the virtual server cannot be extended? I have
removed Sharepoint & tries the installation again, it
results in same error.

Any help greatly appreciated.

Regards,
David.