URGENT: Windows X64, SQL 2005, ODBC - Setting Default Provider For A System DSN

In Windows Server 2003 SP1 (x86) with Sql Server 2000 I could use the following connectionstring no problem
DSN=Hello;

Now I am using Windows Server 2003 x64 and SQL 2005 and I get this error:
Provider is not specified and there is no designated default provider.

If i try Provider=MSDASQL;DSN=Hello; i get
Provider cannot be found. It may not be properly installed.

for DSNless this works fine:
Provider=sqloledb;driver={sql server};server=(local);database=Hello;uid=sa;pwd=p wd;

but i am forced to use DSN as it is in a closed source application which uses set DSNs (the idea there being that you can change the connections how you like in ODBC)

This means that i need the ODBC provider name that will work in here: Provider=...;DSN=Hello;

and then to use whatever works in there as the "default provider" but i cannot find any information anywhere on how to do this!

please reply ASAP!