I wrote about BITSADMIN earlier, use the below command line to directly download Vista SP1. Note that you have to create the c;\download folder yourself or define an other path.
BITSADMIN /TRANSFER VSP1 http://download.microsoft.com/download/3/a/9/3a9b72c2-527d-4694-8a49-84c056d4c34d/Windows6.0-KB936330-X86-wave0.exe C:\DOWNLOAD\Windows6.0-KB936330-X86-wave0.exe