2008 V3.1 won't install to Vista x64!

I run Vista Home Premium 64-bit and have recently tried toinstall Solidworks 2008 V3.1 without success. After the largedownload, it went through some of the steps for install but erroredout after choosing what components to install. It says that Vistax64 is not supported. What am I doing wrong??SolidworksAdministration