Few days ago, I have received email from users asking question :How to run 64 bit SQL SERVER 2005 on 32 bit operating system?
NO. It is not possible. 64 bit SQL Server can not run on 32 bit operating system.
It is true other way. SQL Server 32 bit can run on 64 bit operating system.
Read additional documentation on : 64-bit Computing with SQL Server 2005
Reference : Pinal Dave (http://blog.SQLAuthority.com)