Just got some clarification on this.
SQL Enterprise can be installed on Vista. It is not, however, a supported configuration. This means that should you call customer support with a problem regarding this server, they will not help you. Probably they'll tell you to reinstall SQL on a supported operating system and call back if the problem persists.
Now, what was your question on the SQL 2000 on Server 2003 server?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability