Upgrading from SQL Server 2000
SQL Server 2005 SQL Server 2005
Evaluation Express, Workgroup, Standard, Developer, Enterprise
Express Workgroup, Standard, Developer, Enterprise
Workgroup Standard, Developer, Enterprise
Standard Developer, Enterprise
Developer Workgroup, Standard, Enterprise
Upgrading Editions Within SQL Server 2005
SQL Server 2000 Edition SQL Server 2005 Edition
Evaluation Evaluation
Standard Standard, Developer, Enterprise
Developer Developer
Enterprise Enterprise
For more details click here: http://technet.microsoft.com/en-us/library/ms143743.aspx