Easy One(?) Converting Sql05 Statement To Work In Sql Express

Hi, I was handed an old application written for sql05, it has this (kind of) statement:
Dim CommandText As String = "SELECT c.name FROM db1 c LEFT JOIN "

CommandText += "db2.dbo.Users u ON u.iKey = c.key "

CommandText += "WHERE u.cUserName = '" & User & "'"


As you can see, there are two databases, db1 and db2 and this worked fine in sql05, but when I convert each of the databases to sqlexpress, I get this error: Invalid object name 'db2.dbo.Users'.

So how can I make this work in sqlexpress? Are queries across databases not allowed?

Thanks so much for your help!