What version of Entity Framework (EF) can I use in .NET 3.5 and where could I download this older version?
For .Net 3.5 you can use EF v1.
You tried to download Microsoft.NET Framework 3.5 Service Pack 1 from http://www.microsoft.com/download/en/details.aspx?id=22 It should include the first version of Entity Framework (EFv1), as indicated in http: //en.wikipedia.org/wiki/ADO.NET_Entity_Framework .