Version control page in FP2002 not offering "Use external" option

[mikehc]

I have a Win2003 server running IIS with FP2002, and VSS 6.0. The "Use
External" option does not appear on any sites version control pages.

I have:

- checked sites do not allow anon access, only basic auth
- have changed HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SourceSafe\"API Current
Database" to point to correct database
- have reregistered ssapi.dll
- given everyone full access to c:\vss folder
- ensured that admin and logged-on user account have r/w access to the
correct database in VSS and that the passwords are the same

Can anyone help?

Mike