If you have tried to run VSSConverter as part of an automated script, you’ll know that it’s not obvious how to stop it prompting for the Visual SourceSafe repository’s administrator password.
Eyal points out that you can set two environment variables to achieve this behaviour:
VSSConverter.exe Migrate migrate_settings.xml
Although I haven’t tried it, there’s a suggestion on this thread to try the VS2008 SP1 version of VSSConverter as it’s “vastly improved”.
Note: These options are undocumented and unsupported. They are intended for internal testing. They should work with current versions of VSSConverter, but they’re not guaranteed to work for future releases.