Microsoft SQL Server 2008 Express SP1 (x86 & x64Wow) on 64 bit Windows 7

Installing "Microsoft SQL Server 2008 Express SP1 (x86 & x64Wow)" prerequisite fails on 64 bit machine unless I specify /X86=1. The /X86 option is not valid for a 32 bit OS. I need to be able to install our 32 bit application on both 32 bit and 64 bit OS

community.flexerasoftware.com