If I were to swag this, my guess is that you're not running that on a system
that had WSS 2.0 SP2 installed on it.
SP2 added the additional alternate access features, and this error is noting
that PRESCAN is expecting that method to be there, but not finding it.
Two ways to check, goto the WSS bin folder<%Program Files%>\Common
Files\Microsoft Shared\Web server extensions\60\bin on that server and look
at the version of STSWEL.DLL or STSADM.EXE, that will give you the version
of the binaries installed
Otherwise, you can go to WSS Central Admin and look at the version noted for
the virtual servers.