When you Creating Database Snapshot on SQL Server 2005 Standard Edtion you will receive the following error message. This feature will available on SQL Server Enterprise Edition only.
--Error
Msg 1844, Level 16, State 1, Line 1
Database Snapshot is not supported on Standard Edition.
-- Script to Create Database Snapshot
CREATE DATABASE NorthWindb_test_Snapshot
ON ( NAME = N'NorthWindb_test_datafile',
FILENAME = N'C:\MSSQL\Data\NorthWindb_test_Snapshot.snap' ) AS SNAPSHOT OF NorthWindb_test;