This linked server definitions is working !

EXEC sp_addlinkedserver 'RDBSvr',

   'Oracle RDB Driver',

   'MSDASQL',

   'OracleRdbTest1' -- system dsn with all the nifty details

GO

EXEC master.dbo.sp_addlinkedsrvlogin @rmtsrvname=N'RDBSvr',@useself=N'False',@locallogin=NULL,@rmtuser=N'myuser',@rmtpassword='mypwd'

GO

SELECT *

FROM OPENQUERY(RDBSvr, 'SELECT *...

You could off course create your own user defined function.

There are many examples at SSC.

Since you're running an application overauthorized ....

If you make the application-service-user database owner, it will create objects...

just to add...

also avoid using dynamic sql in your procs, because it may be executed in different context.

No once you're on SQl 2005 you cannot go back to sql2000 unless you use DTS / SSIS to script and/or extract all data.

So even detatch / attatch wouldn't work.

I'm pritty much out of options now 

tried that resulting in :

One or more arguments were reported invalid by the provider.

Cannot obtain the schema rowset "DBSCHEMA_CATALOGS" for OLE DB provider "SQL Server" for linked server "(null)". The...

Is sa jobowner ? if not, make sa jobowner.

(in your first post, job was launched by sa)

Did you specify an "execute as " at jobstep level ? (let's hope not)

check out that the service account of your sql agent has the needed authority to read the folder where your file(s) reside.

login triggers are only supported with SQL2005 SP2

Never trust a default. It may change in time .....

afaik .net framework uses repeatable read by default. or at least, that's what I seem...

how about :

use tempdb

go

DBCC SHRINKFILE

('locigal_file_name' , EMPTYFILE 

go

alter database tempdb

REMOVE file 'locigal_file_name' ;

check bol at http://msdn2.microsoft.com/en-us/library/ms189493.aspx