The following bug has been logged online:

Bug reference: 2361
Logged by: Tomasz Ostrowski
Email address: tometzky (AT) batory (DOT) org.pl
PostgreSQL version: 8.1.3
Operating system: Windows XP
Description: windows installer: pg_config not installed when
"Database Server" not chosen
Details:

After installing postgres-8 on Windows only for development using official
Windows MSI installer (when "Database Server" option is unchecked) the
pg_config binary is not installed.

Libpqxx configure script then fails: "PostgreSQL configuration script
pg_config not found". I have to install totally unneeded on my workstation
"Database Server" to compile libpqxx and probably other programs.

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match