Problem With MSSQL2K5

Hi friends,
I am testing a web application which uses database backend of SQL 2K. Right now we are upgrading the database to SQL 2K5.
For this I have taken a backup of data in SQL2K and trying to restore it using SQL 2K5. It gets restored but browsing the application displays following error.

Microsoft OLE DB Provider for SQL Server error '80004005'
[DBNETLIB][ConnectionOpen (Connect()).]SQL Server does not exist or access denied. ?, line 0

Can anyone will help me to overcome this problem?

Thanks in advance.

Avadhoot