Are you installing named instance if yes, you have to create the alias...
And also check the following webcasts...
Troubleshooting SQL 2000 Virtual Server and Service Pack Setups for Failover Clustering
http://support.microsoft.com/default.aspx?scid=/servicedesks/webcasts...
TechNet Support WebCast: How to install a Microsoft SQL Server 2000 virtual server
on a Microsoft Windows Server 2003 cluster
http://support.microsoft.com/default.aspx?scid=kb;en-us;888121
MohammedU
Microsoft SQL Server MVP