I'd suggest Microsoft support, but SQL 2000 has been out of support for 3 years or so.
Maybe reinstall SQL and reattach the user databases, but I don't know if that will help. Probably a good idea at this point if you get a competent SQL consultant in to help.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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