Oh finally I am able to get Visual Studio 2008 SP1 Beta installed. Been trying to do this since 3 days ago. Thanks for Andre Ziegler that my installation problem is caused by the bootstrapper and pointed me to download the full installer which I guess is made available later after complains from users like me.
That full installer is only the .NET Framework 3.5 SP1 installer (its about 200Mb), for the Visual Studio download, I used the bootstrapper to download everything into my hard drive first (which takes another 500Mb) using the following command.
VS90sp1-KB945140-ENU.exe /createlayout c:\VS90SP1\Layout /passive
Now is to get SQL Server 2008 Feb CTP running in the same VPC. Then hopefully lah I will be able to do some talk on this service pack next month.