I have a server with multiple instances (MSDE and SQL Express). I run the same exact code on both and the correct value for BackupDirectory came back as if...

This is basically the command that is issued when you get the property via SSMS:

DECLARE @smoBackupDirectory varchar(250)

EXEC master.dbo.xp_instance_regread N'HKEY_LOCAL_MACHINE', N'Software\Microsoft\MSSQLServer\MSSQLServer', N'BackupDirectory', @smoBackupDirectory OUTPUT

PRINT @smoBackupDirectory

GO

This should return the BackupDirectory key...

Someone else mentioned drivers with respect to Linked Servers. I have run into that issue. The provider driver must be 64-bit for it to work with SQL 64-bit....

You could also use CONVERT(char(7), date_col, 120) to return a value such as 2004-05.

Caine

It doesn't appear that you set @InvoiceNo, which is used in the WHERE clause of each subselect.  It probably should be tbilling.billid and not @InvoiceNo.

Caine