Slow Recordset

Hello everyone.

I think i've got a big problem developing an client-server aplication.
On Server side I use a postgress sql server  for linux, using SuSe 6.3
distribution, all over a ethernet network with aproxmately 10 clients.
On clients side, i use windows 98 and Visual Basic 6 clients programs
using ADO throught odbc  (postgress odbc driver).

All run ok. I create a database and 5 tables on Access to export all
throught odbc to Postgress Server. Export work ok, and all registers
apears ok. The primary key is exported correctly too.

The table has aproximately 15 fields with one of the of type 'text'.

The i run on Visual a program to fill the database with 50.000 registers
with ADO. All run ok, but when on client run a query like "select * from
alumnos order by codalumno;" over all registers, the query spend aprox.
35 seconds. The server is a Pentium III, 128 Mb RAM, 8'4 UDMA 66 IDE
disk.

I think there must be an error on postmaster daemon runing because its
imposible to run as slow as i see.

Must optimize the database with a view or something like that?
Is this normal?
Need more indexes? (I've only the primary key)

Please, I need help as soon as posible.