Ummmm, which installed packages are you referring to?
If you mean the required system executables (or packages including
executables) like guile, wxGTK, etc, then the installer looks for the
packages by executing one of the associated commands
(e.g. guile-config). In this case, the installer finds the packages
as long as the executable lives in your normal $PATH.
If you mean a required system header file (readline.h), then I believe
that the installer looks in /usr and /usr/local. SuSE likes to put
stuff in the non-standard /opt hierarchy, which can cause some
confusion for some packages. (I have included searching in /opt for
some, but perhaps not all, packages.)
My advice: I have heard rumors that SuSE9.3 includes all required
packages, so you should just upgrade to SuSE9.3 if possible. SuSE9.0
and 9.1 were total nightmares, IIRC, and should be avoided since they
didn't come with the required header files for lots of things.
Stuart--