I think the last version that supported Windows 2000 SP4 for conversion is vCenter Standalone Converter 4.01 and that may not be available for download anymore within VMware.

If you are concerned about outside sites (through internet search) that offer it for download this thread at least has a screenshot of the original MD5 checksum if you want to verify that it has not been modified.

Re: vCenter Converter and v4.0.1 download?