PostgreSQL ODBC driver not showing up in Control Panel (Data Sources)
Did you perhaps install a 32 bit driver?The applet starts the 64-bit version of the odbc admin tool, odbcad32.exe. Try running the 32-bit version in %systemdrive%\Windows\SysWoW64\odbcad32.exe.
Registry redirection makes this a bit of a headache, see http://support.microsoft.com/kb/942976 for more information.